I understand, but that still doesn't justify it. You can deny Harkon and leave when you first go there. That's where the questlines split. The people that side with Harkon should be the only ones able to turn into vampire lords.
Well...In that case, I can offer this bit of wisdom...
*pulls out his megaphone and puts it to Big Punishers ear*
IT'S A SINGLE PLAYER GAME.
*puts it away*
...What some other schmuck does in his game, no matter the choice is their business...Getting all bent out of shape over something that impacts you only merely emotionally, is a personal hangup, and offers no wisdom or value.