Discrimination in the Workplace

I work for a small company (60 people) and a year ago we had this young man join the team. He's 21 gay, married, and a wonderful guy.
Our owner is a stereotypical toxically masculine person and we have all noticed some passive aggressive anti-gay behavior plus a few things that might be illegal.
A few of us have done a bit to be supportive but I am almost frustrated that he isn't more outraged than he is. Like, we were going to boycott the company Christmas party after we found out his husband wasn't invited but then we found out he was going to come on his own anyway.
What's the healthiest way to be supportive given that the actual individual who should be outraged doesn't appear to be?