Why the white king can't take the black bishop? the rook is already pinned anyway

Jump to move 26. The bishop is checking, white king can't take the bishop because of the rook on F7, but the rook isn't really defending the bishop since it's already pinned by the white queen to the black king.
Can anyone explain why such a ruling exist?

Pinned pieces still attack squares/pieces they could even when not pinned and one of the fundamental rules of chess is that a player can never make a move that puts their king in check.
Assume kings could be captured, if you were allowed to take the piece, putting your king in check, then your opponent would have the same rights and could take your king ending the game before your piece could react.

This actually made my brain hurt for a good ten seconds.

You know how checkmate always ends the game, even if the opponent could take your king right after you (hypothetically) take theirs? That's basically how this works. If it were a real-life battle, it'd be a draw, but chess is weird. I guess.

I see... that makes sense. If the black king take the bishop, the black rook will take the white king before the white queen take the black king