"The essence of the Liberal outlook lies not in what opinions are held, but in how they are held: instead of being held dogmatically, they are held tentatively, and with a consciousness that new evidence may at any moment lead to their abandonment." -Bertrand Russell
I think that THIS speaks to aspects of the 'liberal' mindset that are criticized as being accommodating, flexible, dogmatically permissive... I truly think that a distinction needs to be made about the differences between free expression of opinion and judgement. Opinion is of course based on our experience and processing of available factual inputs. Judgement springs from the same well but is more inclusive of value determinations and reveals a response based on egocentric frames of reference.
When we on the left point out instances where words move beyond expression of opinion, we do not do so to suppress speech but rather to encourage a less rigid dialogue. I do think it is healthy to process what we observe against a backdrop of thoughtful and intelligent standards of evaluation, and to express those conclusions. But the conclusions need their backing, and when that backing is based on things like stereotypes, generalizations, assumptions, they reinforce what is inherently flawed reasoning from the get-go.