Again - read carefully if you're so capable - I don't have to "like" either of them. Do you understand that simple statement? I simply have to find one of them so reprehensible, so disgusting, so dangerous that I will do what's needed to prevent that person from taking power.
What about that seems to stump you? If you think there's no difference between Biden and Trump, you're a moran. If you find one of them to be egregiously, beyond all boundaries, worse than the other, then a vote for a third-party candidate provides support for that person you find so utterly objectionable.