The degree of offense-taken, doesn't necessarily reflect the validity of the thought. How a message is received by society, is obviously dependent on the society of that culture. Those philosophers you mentioned, were received in entirely different time periods and cultures. Saying Peterson's message is worse, because more people are offended today, than probably offended in 400 B.C. by Buddha's message, is completely ignoring context and not really a fair criticism.
Peterson gets a bad rap, by people sensationalizing his message and then labelling him as sexist and transphobic.
If you listen to enough of his stuff, you'll realize he is neither of those things (not sure what evidence ever existed of him being sexist), though I can understand why people would think he is transphobic. His original argument against using the non binary gender pronouns is more against legislated coerced speech for people in his position in particular (a professor at an Ontario, Canada university) as opposed to being against transgender people. That being said, he interpreted the laws incorrectly and when confronted with this point, my own impression is he doubled down on his position by saying he won't use the words as it is a neomarxist agenda to coerce people to use these words as opposed to strictly folks who truly feel they are neither male nor female wanting to be labeled appropriately. Ultimately, he did say that if an individual sincerely asked him to use a non standard pronoun, he would.
Peterson gets a bad rap, by people sensationalizing his message and then labelling him as sexist and transphobic.