

Violence is not inherently bad. The badness depends on the context. So “doesn’t that make them more-violent??” appeal is technically true, but that doesn’t mean it’s wrong.
“Cutting someone open and taking out an organ” is pretty fucked up, unless it’s in a hospital and they’re removing an appendix so the patient doesn’t die.
Punching someone in the face is usually bad, but if that person is planning to go on and do mass murder, it’s still in the black.
How do you tell they’re a nazi? Well, sometimes they tell you. Sometimes they wear a clothes that signal it.
Sometimes people act like “if you can’t write an algorithm to perfectly decide how to behave in all cases you’re wrong” and that’s just not how human behavior and decision making has ever been. People make judgement calls with incomplete information all the time, and that’s okay.
Short answer: If they don’t know anything else about you except you’re “Christian”, they don’t know if you’re like a left-wing unitarian or a horrible “conversion therapy, make being trans a felony” evangelical. The former is pretty safe, but if you’re the latter hanging out with you could be dangerous.
Longer thoughts: Many christians are not good about queer topics. This can include “we should torture them” (“conversion therapy”), laws that make life harder for them (eg: banning marriage), and lower grade unpleasantness like “i’ll pray so you don’t go to hell”.
Many christians also don’t really do much to stop their peers. It’s not really your responsibility to fight everyone on every topic, but if you keep going to a church that wants to oppress queer people, you’re supporting something that’s hostile. I don’t care how nice their pastor is or how much fun the choir group is, if the church wants to rip apart my friend’s families and you support that, we can’t be friends. Find another church.
Lastly, and this is more general and less about queer folks, most christians are not very good at it. The bible has lots of stuff about love your neighbor (and your neighbor includes your out-group) and not fixating on material wealth, but I see a lot of so-called christians doing squat for the homeless and vulnerable, voting for cruelty, and sitting around in their nice house with their big screen tv. (All that prosperity gospel, “sin all you want and be forgiven” stuff seems like nonsense.