No one's forcing people to play the game, the issue here is: is it legitimate to waste other players' time base on one's discretion of counts as legitimate game play in Open mode.
In Open, there is tacit consent to potentiality of all kinds of legitimate encounter, the question here is whether when the chance is actualized, people can nullify and break the interaction or not.
Back to the same old fairy-story about tacit consent, I see. It is a lie, plain and simple. You read the EULA (or not, but that is your problem). You buy the game. You click on open. You play in open. You leave when you feel like it. No consent asked for. No consent given. A lie. And always a lie, no matter how many times you repeat it.