I think that the issue is less cultural and more socioeconomic. Being "other"ed your entire life sucks. Making it in another country with far more limited resources sucks. It's hard to ignore the toll it takes on the people I interact with.
You can look at it like that. Another way to look at it is those accepting countries possibly saved your life (if you're claiming you're a refugee) or in the very least gave you a much much safer existence and better healthcare and standard of living. And it's really quite a big expense on the hosting countries who aren't doing that great themselves lately.
The socioeconomics explanation irks me - when you accept a refugee / low skilled worker they are almost by definition going to be poorer than the locals. There's absolutely no way you could equate their wealth to the locals. This is no one's fault, just the reality of taking in people from poorer countries and/or with low skills. I'm also not sure it's fair to say poorer immigrants are always more violent (you didn't say this but it was implied); immigrants from Thailand, India, Philipines into Europe are actually underrepresented in crime. So yeah , this is complex I agree.
Economic migrants didn't have their lives saved. They were not welcomed to their host country as an act of charity. The conditional and transactional nature of their presence is made very clear to them.
There's lots of people who are not refugees and getting into Europe. They can come from places like Morocco, Turkey, Somalia or even Syria as it is now. The strict definition of refugee won't apply to many of them - yet they are able get in and stay (how is another discussion). The best definition would be economic migrant - they are not fleeing immediate war, their main motivation is getting a better standard of living. I have no idea who you're working with but the definition refugee / legal migrant is not enough there's a lot of in between. Is it crazy to expect at least a little gratitude from such people, or in the very least no hostility ? To me it is not crazy, you can disagree.