I think they are less tolerant, yes, and they are less tolerant in a different way than older generations. The Silent Generation (it wasn't really Boomers who were obsessed with this, hell, they were all smoking a ton of dope) wasn't as much about censorship of ideas as Millennials are. What Old School folks really didn't like specifically was obscenity. No foul language (e.g., cussing), no nudity, no depictions of sex, etc. They were/are prudes, for lack of a better term. They wanted those things suppressed, but it wasn't about suppression of ideas as much. If you had ideas that they disagreed with but didn't cuss, weren't "uncouth" in their presentation, etc., they'd still disagree with you, but they wouldn't demand you be silenced. People like my mother-in-law, basically. More concerned with appearances as opposed to how things actually are.
Millennials are not prudes. Far from it. However, they do have sympathies for the suppression of ideas that they disagree with. It is a very pervasive opinion on college campuses, and among younger people I know, that making college a space where nobody is offended is more important than making college a space where all ideas can be aired.