Originally a comment by Screechy Monkey on Exploiting what looked like a principle of free speech.

We live in a world of finite resources, including credibility. Every time you give someone a platform, you are spending some of those resources, whether it’s the physical space, the staff time, the speaker budget, the attention span of your community, and/or your credibility as an institution.

There are thousands of crackpots out there churning out emails to physicists explaining how they have figured out that Einstein Was Wrong, that their pet Time Cube Theory or whatever explains life, the universe, and everything, etc. etc. And free speech demands that they are allowed to operate their badly-designed web sites without being shut down by the Grand Council of Physicists or whoever. But that doesn’t mean that they deserve broader exposure. All of them would be delighted to be invited to give a seminar at Prestigious University’s Department of Physics, and would forever brag about it afterward, and naive third parties would think “well, this guy was invited to speak at P.U., he can’t be a crackpot!”

There are multiple considerations at work aside from just the merits of the proposed speaker’s views, of course. Sometimes a ridiculous view is so popular that there is a real need to expose it to rigorous criticism — the value in having current believers hear the criticism outweighs the cost of potentially exposing more people to the nonsense. Creationism arguably falls into this category, though I think it’s very case-specific: the balance would be different for a small college in the Bible Belt than a prestigious research institution.

In a just world, Donald Trump would have so little support that Joe Biden could safely ignore him and cruise to a general election victory. That’s not the world we live in, so (assuming they are the respective nominees), Biden will have to at least be willing to debate him (though I would not be shocked if no debate occurs because they can’t agree on the rules/format). But that doesn’t mean that Biden should elevate RFK, Jr. or Marianne Williamson by debating them. (And in fact, I’m not aware of any incumbent president debating a primary challenger.)