- "What color are creatures in the Forgotten Realms?"
- "How old do humanoids become on Faerun?"
- "Is being left-handed in the Forgotten Realms seen as weird?"
All these questions should rightfully be closed as 'too broad', considering the Forgotten Realms are vast. There is no way to list the color of every creature, the age of every type of humanoid and let's not even get started on creatures with more than two hands for the last question.
Yet this question remains open: How common is homosexuality in the Forgotten Realms?
The question is, quite frankly, far too broad. It depends not only on the country (a human from Chult likely has a different view on it than somebody from the Sword Coast), but it depends even more on the species. Surface elves are very accepting of the practice, while orcs put such a strong value on men having sons that it seems likely that homosexuality would be a sign of weakness.
The top rated answer, while being great advice for general table-top policies to make certain everybody is comfortable at the table, doesn't even really address the actual question, instead quoting a few lines form the player's handbook that aren't Forgotten Realms specific.
This answer would be perfectly answereable if it was more narrow in scope. The original poster is asking about a gay human wizard, visiting a large sized city. In most cases for the Forgotten Realms, this'd likely be something on the Sword Coast; Neverwinter, Baldur's Gate or Waterdeep.
The question "How is homosexuality considered in metropolitan cities in the Sword Coast?" is a great, answerable question. "How do all the different cultures and species in the entirety of the Forgotten Realms consider homosexuality?" is not going to be answerable comprehensively without writing a 90 page manual.
Yet for some reason, this question remains open. Why?