Is it normal to feel disgusted by the mentally disabled?

Yes, your reaction is actually centred in biology. People with serious mental retardation are genetically defective, prone to violence and strange looking. Your gut for lack of a better term is telling you to stay away from a poor set of genes and unpredictability. Animals in the wild, kill deformed or useless progeny because their instinct is not over ridden with social guilt. All arguments for keeping such ''people'' alive are usually if not always emotionally, based. Also being gay is not a threat to the gene pool, so any heterosexual person disliking you for that reason is down to conditioning not biology. In fact, heterosexual men should be happy you are gay, it leaves more opportunity for them to acquire better life mates. I know very few women, who are prejudice against gays; because usually they are not sexually threatening. What is most disturbing is the fact that our inherit biology is over written by 20th century do- gooding ideals.