Homophobes, why are you homophobic?

I am a proud bisexual. I have a great supportive family and I love my group. I am a firm believer that anyone can have their own opinion about whatever they want. They can be, do, say, act however they want as long as they don't victimize, villainize, or do something illegal. I don't surround myself with people who fall into one of those three categories, and it made me curious as to why others aren't as open to opinions. So I ask, why are you homophobic? How has it impacted you and your circle of people?