The last line was meant to offend. That's a classic line for someone who is being prejudice, but justifies it because they know someone who is of the group they are being prejudice against. Hence my comment about my black nephew.
That's complete and utter nonsense which shows your lack of intelligence. You are making the same type of generalization as you are trying to be opposed to. Most times when someone says they have a gay or black friend, it is because they want to show that they have experience with the situation and obstacles they deal with. You are very rude for attacking someone for mentioning that. Someone who has not been exposed to a person they knew was gay may have a false idea of gay people. They might think they are all very nice, funny, fashion conscious people as they are portrayed on TV. Those who have been exposed know that they come in all types just like straight folks.