"After the introductory meeting, my white colleagues started questioning his skills." You know, as I do, that this is blatant racism. That is what you wrote. I faced blatant sexism in the Navy as a female in a male-dominated rate (MOS). My skills were constantly questioned. I'm a fighter. So, I fought back in numerous ways. I learned some mad skills in reference to dealing with blatant anything.

Fake crying. Oh do I hate that. I hate any female ploys used to get their own way. I call out my fellow females when they pull this and other things.

You are upset with yourself because you didn't do anything. Don't blame yourself. You were, obviously, outnumbered by racist white people. If I were in your shoes, I would have found another job then started a social media campaign to show how racist this company is. That's what really needs to happen. I review bad companies at major review sites for that very reason. You would be amazed how much business they can lose. If you don't work there now and it hasn't been long since you did, you can still do this. Do so as a way to confront racism. This is very powerful.