Why was this useage of "queer" offensive?

In the context used in the modded post, it sure looks like it is being used offensively.

I got the flag, I debated if a note or warning was merited. I checked some things on the board and Googled queer. First thing in the definition was OFFENSIVE. So based on this, I issued the warning. Context was the most important part of my decision.

Obviously I am willing to listen to why I might be wrong.