He said that to you because he was angry and hurting. He needed to lash out at someone, you were nearby and an easy target so he took out his frustration on you instead of facing tougher targets like actual Trump supporters/voters.

Not even Donald Trump being elected as president of the US is going to stop LGBT infighting and oppression Olympics. Who has it worse, who can pass easier, whose suffering matters more, who is going to get screwed over the most, etc etc etc.

The challenges bisexual people face is never taken seriously by anyone ever. There's no doubt that yes, there will be bi people who are relieved they can pass, as well as gay, lesbian, and trans people relieved that they can pass as well. That's the reality. But no one cares about the bi people who can't pass or have no wish to do so or are absolutely sick of it. Our voices never matter.

He's your friend and it was the heat of the moment; feel free to let it slide, but keep in mind you're probably going to come across that attitude a lot more often because that's what many gay men and lesbians really think about bisexuals. It's nothing new, but with tensions running high, it'll be more prominent.