Today in plenty of reasons:

If you don't like the protests, maybe
hand down less egregious rulings?

"...simply because people disagree with opinions, is not a basis for questioning the legitimacy of the court."

-Chief Justice John Roberts

on why every should just be cool

This was a part of some comments he made about the Supreme Court being reopened to the public after COVID 19 and after the national outcry over the reversal of Roe v. Wade. 

And fine, he's correct. Disagreeing isn't enough, but just to be clear people aren't protesting and questioning the legitimacy of the court because they've been handing down decisions disagree with. I mean, ok, we are and they have been, and I actually think that disagreeing with something is a totally valid reason to protest, but whatever, it's not just that. 

Also, there's disagreement and then there's outrage at the stripping
of a fifty-year legal precedent and fundamental right. It's not like we're
disputing a credit card charge or a parking ticket. This shit matters.

All we knew for sure about him is
that he likes beer and cries a lot.

We're also questioning the legitimacy of the court because three of the last four appointments are questionable. Either way you look at it, Mitch McConnell straight up stole either Neil Gorsuch's seat or Amy Coney Barrett's. With Gorsuch's he argued that it was too close to the election to let Obama appoint a justice. And then when Ruth Bader Ginsburg died he rammed through Coney Barrett a month before Biden beat Trump. Either one is legit or the other is, not both. As for Brett Kavanaugh, the administration sat on evidence that he may be guilty of multiple sexual assaults.

Among other things.

Also, didn't Kavanaugh and Coney Barrett swear up and down that Roe v. Wade was settled law only to change their minds once they had the job? Sounds a little perjury-y to me. And that's not even touching the fact that Ginny Thomas, sitting Justice Thomas's wife, pressured lawmakers to overturn the election. All this on top of the fact that Gorsuch, Kavanaugh and Coney Barrett were all appointed by Donald Trump; someone most Americans voted against--twice--and who flushed the centuries old tradition of peaceful transfers of power down the drain.

Look, we're not a bunch of whiners who can't accept election results, we're the majority of the American people who have watched helplessly as the court was stacked by someone now facing charges for actual crimes. We're not questioning the Supreme Court's legitimacy just because we disagree. We're questioning it because a third or more of the court's justices are eminently questionable. At best. Legitimately illegitimate at worst and we're stuck with them until they either die or retire. So yeah, we're angry and going to let them know it.

Get it? Because the--look, it's not the cleverest slogan, but it's also not wrong.