They view this as protecting themselves and their families from a lifestyle that they believe to be immoral and destructive,
If we cannot have moral feelings against homosexuality, can we have it against murder? Can we have it against other things?
Burning the flag is a form of expression. Speech doesn't just mean written words or oral words. It could be semaphore. And burning a flag is a symbol that expresses an idea - I hate the government, the government is unjust, whatever.