Just because a person is anti-gay doesn't mean they believe in God. It doesn't mean they even agree with the hate group leader in his opionion about Natural Disasters punishing gays. If anything, those who did believe this will only alter their belief to say something different. I don't think this will change their opinion or deep seated beliefs about gays. It's going to take more than that.
Anti-gay protestors can find plenty of reasons to explain why God has acted in this way. They talk about how this is all part of God's will and how this hate group leader is being tested and will emerge stronger. They will no doubt be able to blame it on gays people living in the neighborhood.
No, I doubt that the fact that his home was overwhelmed by floodwaters will change his mind in the direction of acceptance. Since Victorian times people have hated homosexuals. The very word "queer" connotes "different" or "strange." Gay men and lesbian women will always be a minority in our world, and will never be accepted into the mainstream culture.
This man's rhetoric won't calm down because he believes gays are morally corrupt. Just because a natural disaster happened to him does not mean he doesn't believe they can't happen for any other reason. People's thoughts are not limited to one-way or linear beliefs. He probably thinks it happened to him because it was the will of God.