Mass Effect is a fantasy, in reality we would never become that friendly with aliens, especially not in the unrealistically short time frame humans in the MEU do, we would just be too fundamentally different from each other, they wouldn't be humans in costumes like the ME aliens are.
You will find that Ashley's views would be extremely tame compared to the beliefs that most other humans hold about aliens. I can already see the alien scapegoating that will be going on in the mainstream media.
Yes, Mass Effect uses several contrivances to even make it fit.
-The Citadel and mass relay system encouraging travel but also a place of peaceful communication
-Perhaps the concept of evolution (at least in the Reaper sense) preferring 'humanoid' species, and guiding them into power positions
-Asari stepping in and settling a conflict that would have wrecked humanity
A lot of humanity has socially evolved past racism, genderism, sexism, and more. Or at least, is now actively attempting to navigate the way past these things. But still, most of this is able to be done due to the concept of common humanity. Many people will take this figuratively, and carry those lessons on towards hypothetical aliens. But many will also take this literally, and a threat to humanity will be treated just like a threat to one's sexuality, race, gender, religious position, etc.
Mass Effect expands this into the concept of not just species, but technological integration. Should we use technology *only* as tools, no matter what comes our way and maybe even surprises us about technology? Or should we take a regulated approach towards it, and try to harness technology while encouraging its proliferation? Or should we embrace it and go full steam forward, and let go of caution about the consequences? What if this means new forms of life? New species - organic, synthetic, and somethings akin to both at the same time?
We have been faced with 'abominations' and 'husks' throughout 3 games. But were they really? As far as we know so far, they were... but there's been a pattern so far in Mass Effect. Humans hated the turians too. The Council species hated the rachni. Quarians hated the geth. Not all of them, but enough that again, there's a pattern.
How much do you welcome and encourage, before you lose yourself? How much do you tolerate, accept, or embrace? Sometimes this seems very, very clear. But other times, even very specific matters might have you emotional, reactionary, and fighting for what you consider your way of life, and control over your situations and environment. Cult-ure is very important for this.