Na, that questions been asked to death and at that point they had been on the show for 8 years. The crowd didn't wanna hear it (because weve heard all the bisexual head cannons of LGBT fans ad nauseam )
LGBT fans of this show shipped the brothers for years to the extent the show made fun of the incestuous demands of the fans. It also pissed off and grossed out the mainstream fans. They were brothers.
LGBT fans have asked and been told no about dean and Castiel for years and years and years and years that dean is straight but they insist on looking for "queer coding" in a show about family and brothers and there's only so many times you can answer the same question without getting pissed off and it was a waste of a question according to the crowd many of which probably wanted to ask their own questions about the show as it is not waste time on people's head cannons.
It's a show about brotherhood. I swear some people have never had a close heterosexual friend or known close heterosexuals because the second a close heterosexual friendship is on tv they ship it as a couple and have all kinds of tantrums and accuse the actors, writers and producers of all kinds of isms when their head cannon isn't true.
I don't blame him for being rude. How many times can you answer the same question without getting pissed off when that fan knew damn well that Dean's a lady's man.
Cringe