I can see tolerating the Vidiians over the other ones.
The Vidiians were literally being eaten alive by the Phage, so it becomes a desperation issue. I thought their plight was brilliant because you have a built-in moral dilemma for that race.
The ones from "SCIENTIFIC METHOD" were basically just experimenting to get some results faster for various issues. Their need was not as dire as the Vidiians'. Plus they were being sneaky about it.
OK I must dig this episode out because I can't remember watching in full.