In online political discussions, I often see the term "tolerant left" (or "tolerant liberal") being thrown about in a derogatory manner. It usually occurs when someone - regardless of political viewpoint - calls out prejudice. The thinking behind the argument - or rather, insult - is that while liberals regard themselves as tolerant and accepting, left-leaning people can't really be tolerant if they don't respect all other perspectives, even if said perspective involves racism, sexism and/or other hatred.
Being a tolerant person is not something that only people on the Left are capable of; being tolerant means that someone accepts people regardless of their nationality, ethnicity, gender, sexuality, etc.; most common ideologies aren't opposed to different demographic groups. Under no circumstances does tolerant mean that someone should accept and respect bigoted viewpoints; no one should be "tolerant of intolerance".
The "tolerant left" meme is also counter-productive to those who use it as an insult because it assumes that acceptance/tolerance are solely a feature of the Left, which in turn would then assume that bigotry is the default state for anyone on the Right. Therefore, those who identify as conservative but mock "tolerant liberals" are foolishly arguing that their own side is bigoted.
In short, being tolerant - whether you're liberal or not - does not mean that you have to be a sucker and respect bigotry. "Tolerant left" is just a made up term that racists, sexists, etc. all use to deflect from their being obnoxious.
(And yes, I have seen cases of when someone who identifies as conservative calls out racism and/or sexism and has the "tolerant liberal" meme thrown at them.)