What we ought to do and what we are permitted to do depends on the facts, or at least what is reasonable for us to believe that facts are. For instance, if contrary to fact, Saddam Hussein had indeed had "weapons of mass destruction" and imminently intended to use them against innocent targets, the case for invading Iraq in 2003 would have been much stronger. Whether we should punish someone for a crime depends on whether he in fact did it. Whether you are permitted to kill someone depends, among other things, on whether one reasonably believes that person to be an imminent threat. And so on.
Many of the people who stormed the Capitol yesterday believed that the 2020 election was beset with massive fraud. They believed that not only were the rules changed at the last minute or in illegal ways to benefit the Democrats, but also that lots of fake votes were counted, that many legal votes were thrown away. The media and political science researchers might continuously deny that there was widespread fraud in this or other recent elections, but the mob regards them as untrustworthy partisans and as branches or agents of the Democratic Party.
Now, it matters what the facts are and what is reasonable to believe. In fact, there was not widespread fraud and it is not reasonable to believe that there was. In fact, the rules were not (much) changed in illegitimate ways and it is not reasonable to believe they were. So, here the mob was wrong. (As for whether the media or the political science profession are branches of the DP...well, that's closer to the truth.)
However, it's worth asking, what if they'd been right? Consider for instance recent elections in Russia, whether this is strong evidence of manipulation, fraud, fake counting, and other interference with the democratic process. Suppose, contrary to fact, this kind of thing had clearly been happening for a long time in the US, and that it was quite clear this election was fraudulent. Suppose, contrary to fact, that the mob were right; the Congressional "review" of the electoral college results was little more than a bunch of colluding fraudsters depriving the people of their voice. Suppose that state secretaries of state, judges, and election officials were in fact all in cahoots with the Democrats, and it was reasonable for the mob to believe that.
Now ask: If those were the facts, would it have been legitimate or reasonable for them to storm the Capitol yesterday? Indeed, if the facts were different, would you see such behavior as a pro-democratic uprising? (If, say, Hong Kong pro-democracy protestors stormed and occupied the LegCo Complex after a sham election rigged by the CCP, we'd think differently.)
Again, I am not excusing the mob. They have the facts wrong and their beliefs are not reasonable. Many of them don't even really believe what they say; for them, saying, "Trump won" represents not a real commitment to the claim that Trump won, but is equivalent to waving the Steeler's terrible towel at a game. So their behavior was deeply wrongful, illiberal, and anti-democratic in a way that even critics of democracy like me despise.
UPDATE: I notice I wrote "Capital" instead of "Capitol". Should have had more coffee first.