Not reasonable because you’re making a broad generalization
Generalizations are broad by nature, that does not mean they have no value.
But in reality the majority of people who oppose immigration also oppose LGBT+ and freedom of religion so it’s unlikely they’ll use this argument.
Can't speak for the USA but that is absolutely not the case in Europe.
Otherwise you make some decent points. In any case, IMO discussions like this would benefit if we accepted from the outset that nobody is going to be convincing others to change their opinions. The best that can be hoped for is to understand the opposing side better. That would be an achievement in itself.