This is sad! As a francophile, I can report that "biche" is quite a popular word in French that is not used as an anti-gay slur, although some francophones mispronounce the English word "bitch" as something very close to "biche" and use THAT as an anti-gay slur, or term of endearment, depending. But it's not common.
Did you know, by the way, that there's an indirect Brazilian connection to the current popularity of "biche" in French culture?
Henry Salvador! He was a French Caribbean singer (and superstar in France) who is thought to have influenced the development of Bossa Nova in Brazil, though he was not himself from Brazil.
In the mid 1950s, he released a single greatly outside of his usual singing style, "Le loup, la biche et le chevalier." (The wolf, the doe, and the knight.)
Based on a traditional medieval tale, Salvador's song shot to the top of the charts, and now it's a beloved children's song that pretty much every French speaker knows by heart.
Here is Salvador's original:
https://www.youtube.com/watch?v=R_bmOSlF6f8
And here is a more recent interpretation by the divine Celine:
