You mean these quotes.
"We created an intelligence with the mandate to preserve life at any cost."
"The intelligence has one purpose: preservation of life. That purpose has not been fulfilled"
These came straight from the horses mouth, the catalyst was in fact designed to preserve life.
Provide evidence that the catalyst mandate was specific to the Milky way. At no did the mandate specify the milky way in particular it was just "preserve life" something that can broadly interpreted.
Do you know what context is? Do you know that context can change the meaning of words, in fact context can take a group of words and actually have them mean the exact opposite. "Joe is so smart," sounds like someone is saying a person named Joe is intelligent, but the context could be that the person means the exact opposite. Joe claims that a tin foil hat will keep the aliens from reading his mind. So Cindy says in a mocking tone, "Joe is so smart." Context is "everything" to meaning.
CONTEXT is as vital if not more vital to a determine a conversations meaning than just the text.
Here are some pieces of evidence that we know about the situation of the galaxy with regards to the Leviathans, the catalyst and the other races in the galaxy at the time catalyst was created.
Leviathan were the apex of life in the GALAXY. Lesser life forms were in our thrall, serving our needs. (This establishes that the other races there servitors to the leviathans and note makes this statement in the context of THIS galaxy only. This single statement provides the context of what SCOPE the leviathan is speaking of for the entire conversation.)
Source: https://youtu.be/lEqlG6bhZ80?t=2m26s
Leviathans grew more powerful but the servitor races could not be saved from themselves. "Over time, the species(note the plural) created machines that then destroyed them. TRIBUTE does not flow from a DEAD race." (The problem is not races are dying or killing themselves off the problem is you get no tribute from a dead people. This is the second piece of evidence for the CONTEXT of what the leviathan is telling you.)
Source: https://youtu.be/lEqlG6bhZ80?t=2m33s
"To solve this problem,..." (Note you are specifically told right after, "tribute does not flow from a dead race." that this is the problem. So the REASON the catalyst is created is NOT to preserve life. It is created to keep tribute flowing by preserving the life of the servitor races. This is a non subtle difference. In one case the mandate is to preserve life in another the mandate to maintain tribute by preserving life. It is this "distinction" that allows for the harvests. The harvests don't make any sense if the mandate is to preserve life period. They make perfect sense if the mandate is to preserve life for tribute, because the harvests become the ultimate representation of the tribute system. The reapers take all of a race's knowledge, technology, genetic material, resources and history and "preserves" it in the form of a new reaper under the command of harbinger the first reaper who was created from harvested Leviathans. When the preservation of life is to maintain the tribute system, creating "organic living goo" for the next set of reapers to serve the Leviathan reaper Harbinger makes sense. Yet if the mandate is just to preserve life for its own sake then the solution makes no sense.
let us continue...
"To solve this problem, we created an intelligence with the mandate to preserve life at any cost." In fact you use this quote but you seem to have DELIBERATELY removed the first part of the sentence, 'To solve this problem," and you don't quote it like this either "...we created an intelligence with the mandate to preserve life at any cost." Which would indicate that you are not quoting the whole sentence, no you quote it in a manner that deliberately misleads the reader, because the entire context of what the mandate is, is in reference to the statement, "Tribute does not flow from a dead race.To solve this problem,..." Context is so vital for meaning.
Source: https://youtu.be/lEqlG6bhZ80?t=2m51s
"As the intelligence evolved, it studied the development of civilizations. Its understanding grew until it found a solution." A solution to what? The "problem." Which was what?
"Tribute does not flow from a dead race."
There can be no misinterpretation as to what the problem is and to what the solution is for. The solution isn't to preserve life for life's sake it is to preserve life to keep tribute flowing.
Source: https://youtu.be/lEqlG6bhZ80?t=3m1s
We are then told that the catalyst "betrayed" the leviathan race and that they were the first race harvest creating the first reaper harbinger. This further strengthens the argument that tribute is the key to the entire reaper cycle.
https://youtu.be/lEqlG6bhZ80?t=3m10s
Again we get a FURTHER confirmation that the scope of the Leviathan's perspective on the problem was galactic not larger.
"You cannot conceive of a GALAXY that bends to your will."
This statement reaffirms the context of what scope the entire conversation is about, what scope they created the catalyst to preform within. How do we know this? Because this is telling us what perspective the Leviathans are viewing their situation and problem from. And it is clearly GALACTIC.
https://youtu.be/lEqlG6bhZ80?t=3m29s
"There was no mistake. It still serves its purpose."
And that purpose it to keep tribute flowing. We know this because this was already identified as the PROBLEM in the conversation and that the catalyst was created for this solution. So if the catalyst is doing what it was programmed to do we can infer that the entire harvesting cycle is to provide tribute to the Leviathans in for form of Harbinger.
https://youtu.be/lEqlG6bhZ80?t=3m52s
Further into the conversation we actually see that the scope of the catalyst itself is LIMITED to the Galaxy created yet a third piece of evidence that the catalyst was looking to create a solution on the GALACTIC scale.
"To find a solution, it required information--physical drawn from organic life in the cosmos. It created an army of pawns that searched the GALAXY, gathering this data."
If the catalyst had a mandate that spans beyond the milky way galaxy then it would have search beyond just our galaxy for a solution but it does not. Why? because again we can CLEARLY see from the conversation the entire content of the catalyst's scope is within out galaxy. We are give very explicit limitations to its scope in this conversation we constantly have the scope commented on within a galactic context.
https://youtu.be/lEqlG6bhZ80?t=4m54s
Everything the Leviathan tells us about the reapers and the "intelligence" is within the context of the above. When it talks about preservation of life it is within the context of that being a solution to the problem of tribute not flowing from a dead race. With this core context the idea that preservation of all life outside the milky way makes no sense when everything about the conversation was talked about on a galactic scale.
Did the reapers have the capability to reach other galaxies? Yes but their mandate was limited to the Galaxy and this is confirmed multiple times in the conversation and once specifically speaking about what the catalyst does to solve the problem.
Here is the evidence. Is it proof? No but i always said "evidence (not proof)" when stating there is evidence that the reapers are confined to the milky way.
So I again ask you what evidence do you have that the reapers are extra galactic in scope? You asked me for my evidence and I went into considerable detail providing it. Why do I doubt I will get anything close to this level of response back?
Anyway it is very late so i will stop here and maybe break down further conversations about what reapers do between cycles. To further show the scale to be GALACTIC. And yet i doubt it will change anyone's mind because most people are opinion based not evidence based.