It is a distinct misunderstanding of tolerance to believe that everyone is right in some way, so one can never criticize other cultures or times. (And I will never remember the correct spelling of "criticize").
If someone claims that the rabbit is a ruminant, then this person does not have "another kind of knowledge" or "another cultural background" - that person simply holds a wrong belief about a positive, provable, objective fact. What is wrong, is wrong, plain and simple.
And pointing this out does not mean any disrespect to said person. To the contrary - letting people believe bullshit just to be polite or not touch on any sensibilities means not accepting the other person as a grown up, self-responsible being. Whenever I do so, I'm not really protecting the other person - I'm just protecting myself from her anticipated reactions.
It is necessary that we let go of our attachments to belief systems. And for that, we need other people's criticism. Otherwise, how will I ever realize how attached I am to a belief? And how will I ever find out when I'm wrong?