Conceeding and Play To Win

Does being compelled to keep having to participate in a game where two players have agreed to ensuring your demise, give you the right to concede, or are you instead forced to sit at a table until they have decided they are finished toying with you, even if that might take a while?

An example:

A 4 player table has the following:

PA - Playing a Political Deck with vote Lock
PB - Playing an infernal deck at 1 pool.
PC - Playing a bleed deck with 0 stealth and 2 minions.
PE - Playing a deck with 2 Vampires with Guardian Angels

Player C already ousted Player D and player E is unable to generate enough intercept to stop player A.

PA has made a deal with PB to give away 1 VP because player PC has more ability to oust PA than PE can.

However, PC knows that if he self ousts before that, PB will have a better chance of overtaking PE and getting 2VPs instead.

PC already has 1GW and 4VPs from prior tables.

Does PC have a right to self-oust, or would that be ruled "Not Playing to Win" and "Unsportsmanlike?"

I will only comment on how I see the situation in regards as how the Tournament rules are written.

The only important thing in regard to the "Play to Win" rule in the tournament rules, is the state of the game, the result of previous games are not relevant, unless it is the finals, since seed is a tiebreaker in that case.

"Conceding" in the sense at is written in the tournament rules is only possible if all but 1 player want to concede, usually done when there is only two players left.
this is always possible and overrides the "play to win rule" (Rule 3.5)

Besides that, if the player is convinced they can't make anymore VPs, due to the state of the game alone, they are free to oust themselves.
While the other players may argue that fact, all they can do is ask for a judge, who will look at the state of the game from the perspective of the player that is accused of violating PtW and the current board state. If the judge seems it possible that the player might thing another vp is impossible from this board state, the player is free to out themselves.

In my reading "unsportsmanlike conduct" would only be the case, if the player would oust themselves, from an obvious winnable position.

Regarding your concrete example, it seems reasonable that player c sees themselves blocked for both actions, and if they know that there is not enough stealth left in the deck to oust before they see themselves ousted, and not seeing themselves surviving to timeout even if not acting, they are, in my opinion free to oust themselves, purely from the tournament rules Perspective.

Always remember, PtW rule doesn't mean "making the wring decision" is against the rules.