*reads thread and headdesks*
Here's the problem with us being racist/specist space conquistadores, OP: I find it extremely unlikely that when selecting candidates for the ARK, the selection committee (one would assume that there was one and that there were specific criteria for the candidates if this was a long-term project and not something hastily thrown together) decided that the top candidates should include racists/specists and pro-human Cerberus rejects.
This is a group survival effort, and you probably want only the most psychologically stable (and intelligent!) beings who aren't specist or racist, because everyone is really going to need to get along and co-operate. I'm not against someone getting mad at an alien NPC and dropping f-bombs or using elaborate and colorful epithets in a scene of intense emotion, but come on!!!! Who in their right mind would ship off anti-alien bigots or human supremacists...with a bunch of aliens. Logic much? Hmm, BSN forums - I suppose logic doesn't often apply here.
You're just setting up your future civilization(s) for potential conflict and possible self-annihilation if you're not screening to keep out people with negative personality traits. I expect things might be enough of a powder keg as it is if the ARK people have limited resources in the beginning. Just read the novel Seveneves to see how things work out for the human race after a catastrophe that pretty much ruins the Earth and forces a small number of survivors to flee into space. Spoiler alert: they almost wipe themselves out and end up with only seven people left, DESPITE everyone being of the same species - only barely surviving to repopulate through genetic tinkering to create new races based on each of the seven survivors.
If you want your future space colonies to fail, sure, you pop all the bigots/racists/specists and wingnuts in that you like - let's see how that works out for you! And even if everyone's not living together and has their own ships, well, you're not going to win friends and keep the peace by having your character be a racist/specist d-bag. Under normal circumstances in some relatively stable game world/universe, I wouldn't actually care if someone wanted to play a racist/specist/bigot. However, I think ME:A puts everyone in a situation in which it would be the height of stupidity to send those kinds of people off as the best hope for everyone's survival.