I'm not sure why people think that anyone saying voting for Biden is going to be a problem is ok with Trump.
Maybe the issue is that people see this as a binary short term situation. But it's not particularly. The choices avaialable to voters will have an effect on what happens long term, in many indirect ways, and those may be far more important than what happens directly in the next four years.
Trump has no real political program and he doesn't represent one. He's not working for anyone explicitly, he's not in the interests of either party. The biggest dangers he represents are around being incompetent, inability to understand the political and social and economic environment, and a sort of political chaos. Which could be quite bad, but at the end, but it doesn't lead anywhere specific.
Biden wouldn't have those kinds of problems, but his election will very likely prevent the kind of change within the Democratic Party that would prevent another populist from coming to power. It will increase alienation of the group that voted for Trump as well as those who have stopped voting because they feel powerless. It's also very unlikely that it will in any way move towards solving the problems with globalism, jobs, the environment, medical care, violence, or public trust in government.
So what's a voter to choose? Trump, or what caused Trump? Do you really imagine people will vote for someone they know will probably hurt them, even if he's less incompetent than the other guy? And what if people do bite the bullet and vote for Biden? Short term it means more stability, but here is a good chance it will result in more destabilisation in the medium term.
They are fucked whichever way they vote, and a lot of them know it.