Because at some point it becomes a distinction without a difference. At some point you’re sitting there deciding between Hitler or Mussolini. Mussolini might objectively be the better choice, as his crimes are fewer than Hitler’s by pure magnitude. But given that choice, a lot of people will just refuse to participate.

People don’t vote based on pure logic. That’s not how human beings operate. Don’t make your voters feel like they need to go to confess their sins to a priest after voting for your candidate, and maybe then you won’t have people refusing to vote for them.