Can someone explain the secret meaning of the phrase, "that gay thing"?

A friend went on a fiction chat room asking for fic recommendations for a particle character. An author of gay fiction recommended a slash site. The person said thanks but said they weren't interested in reading gay stories or any stories at all. This person got offended and said they should stick to reading only stories about animated characters because 99% of all fan fiction is gay. My friend replied back. I just don't understand the gay thing and why people feel the need to write straight characters as gay. This author then copies the conversation and posted it in a blog claiming that because this person is Christian that they are a judgmental bigot who thinks gays are "immoral and inferior" But my friend never said or even hinted that. The author claims that the statement "that gay thing" implies those beliefs. I have never heard of this and now people are posting nasty messages on my friends page attacking her religious beliefs when she what she only mean was I don't like gay . So why should she be attacked because of an innocent statement?