Your response seems to underline the whole problem I have with the direction this discussion has taken - that a person playing the game differently than you means that they aren't your friend. Both sides have the assumption that any percieved slight in the game has the appropriate response of ending a friendshp.
I don't think the issue is one of playing things differently. It is playing in a way that makes other people uncomfortable and not stopping if they ask you to.
If a friend has his character develop a crush on mine, and I find that odd, I wouldn't immediately try and get him kicked from the game. I'd tell him that it bothers me and ask him to stop.
It is the point at which he decides to either keep going with it, or amp up the uncomfortableness, or try and get in my head to figure out why I won't let him do that, or cause more trouble for me in or out of character in response... that's when I realize he probably isn't a friend, or someone I want to game with.
Basically, if friends are actually resolved, communication should resolve the issue. Even if that resolution is that we both want to be playing a different type of game, and someone leaves the group to play in a different style of campaign while still remaining friends with everyone in the original group.
But yeah, being unwilling to back off from harassing someone in character, or feeling that its an appropriate response to ramp things up since they refuse to 'lighten up'? That's not cool, and certainly not the actions of a 'friend'.