Except he doesn't really have friends or loved ones.
Maybe I have a twisted sense of love and friendship but it doesn't involve killing them and destroying their world because I have a bad case of the guilt going on.
He's not the Dread Wolf for nothing , he is a lone wolf , Solas has no pack , never has one and doesn't want one.
I mean perish the thought , he can't stand people who don't listen to him or don't think everything he says is the truth.
In DAI if you say you respect Sera , or believes Dorian about the time travel , or you'll ask Varric and Cassandra opinions and not just his , or if you'll say you'll rely on your friends after the Well : dude disapproves.
To whom? To the Inquisitor? Remember, his system of values is so vastly differently from those that we would have that we can't say for absolute certain that 'yes, he's shuffled off to wacky land!'. From his perspective, a being who has literally lived hundreds of our lifetimes, the lives of humans may be flash and gone. His concept of time is potentially impossible to relate to. Possibly. I mean, if it was us...humans that is...and we woke up after a Van Winkle to find that humanity had gone from our current lifespan to living only a few short years, and had the cognitive power of a parakeet, we'd react poorly too. To HIS perspective, he is saving his people. A psychopath wouldn't care about that. A psychopath DOES things, for their OWN pleasure, nothing else.
We know from the Fade that his greatest fear is being alone. Dying alone. When you ask questions, he approves. Interest is appreciated. He craves interaction from others. Outside of Cole, his only REAL friend is the Inquisitor if you put the effort into it. As much as he talks up his friendships with spirits, he NEEDS a connection with a real person. Hence his reactions. Now, why he disapproves? Jealousy maybe? Friends GET jealous, though not all show it.
Lone wolves tend to die much quicker than those in a pack. Their life is far more difficult, and makes them easy targets. Solas WANTS to belong.
Solas DOESN'T want to kill people...he feels he HAS to. Again, this is fanaticism. It alters his perception of events, allowing him to step outside his normal understanding of norms and morals to act in a way that would normally be horrific and repellant. Look at a mob mentality. When individuals are in a group situation they can become incensed and act in a way contrary to their moral guidelines because they step outside themselves and allow the group mentality to take hold. Riots, war crimes...many of these things were committed by individuals that would normally have NOTHING to do with those acts, but in the right setting, with the right prodding, they do something repugnant. And that is with OUR current moral relativism. Assuming that an individual of a different culture and race (not to mention time) would hold to our standards is unwise. Solas will follow the guidelines that he has set in accomplishing his goal, no matter how unethical it seems because he feels the value of the end result is more important than his personal set of values.
Now, having said that, it makes it NO LESS of an abominable act, and all efforts should be put forth to halt his plans. Understanding that he is willing to set aside his own morals to restore his people to what he believes their rightful place is necessary if one wishes to stop him. If you know how and WHY he does what he does, it could allow you to anticipate what he will do next. Allow you to find a way to catch him off guard, and show him WHY his rationalization is incorrect.
...or lop off his head when he is distracted. Whichever you are looking for. Point is, the more information you have, and how you are able to understand that information is key in understanding your enemy. You understand them, you can beat them.
Diplomacy...saying 'nice doggie, nice doggie' until you can grab a big stick. And this is a BIG POWERFUL doggie.