FPTP is a winner take all system, and it has been shown that such systems force most people to vote against people they don't like, rather than vote for people they do like.
The surest way for PartyONE to beat PartyTWO in a FPTP election is to have a viable PartyTHREE candidate that PartyTWO likes. If such a candidate can be found, PartyONE will surreptitiously fund the PartyTHREE candidate (who has no chance to win) even though PartyONE hates PartyTHREE, in order to take votes away from their opponent PartyTWO (who has a chance to win). If I would rank the candidates like this...which is common for me:
1) PartyTHREE: love this candidate, and really want him to win.
2) PartyONE: don't like this candidate, but know he is not half as bad as...
3) PartyTWO: hate this candidate--the worst candidate by far.
In the FPTP election, the race is really between the candidate I can tolerate and the candidate I hate. If I (and a few million others in key places) vote for the candidate we love, then we make it more likely that the candidate we hate the most will win.
I know you know all this. This is just strategic voting. I was like you in the 90's, and I was a big Harry Brown supporter. "Who?" you might ask? Exactly. I argued against people who voted strategically, like you are doing now. Obviously, I didn't get very far. I made my protest votes, but they had no effect.
Successful change to a third party happens very rarely, and when it does, the non-changing party usually gets 20 years of control while their opponents regroup. That was OK in the 1800s when the Federal Government didn't actually have that much power to affect people's day-to-day lives. But, 20 years of control by the Dems would be very disastrous for the country. In my opinion, it cannot be risked, so I vote strategically, and not for the my "cult" favorite.
I'm curious which non-D/non-R candidates do you vote for?