The problem is that both sides of this argument are wrong.
You are one of four players in the group. You need to consider the rest of your group. If you and only you want to spacebar through conversations then demanding that the rest of the group do what you do is selfish. On the other hand, you are just as selfish if you and only you want to watch all the conversations.
All of us need to be willing to compromise more.
I agree 100%, and honestly find it rather sad and confusing that this mindset is rare, at least on the forums.
I am in the spacebar camp, and I do frequently politely ask for space bars if it's a flashpoint with a lot of dialogue like Black Talon. But if someone doesn't respond or says they don't want to space, I just roll my eyes and don't say anything further. I personally find it annoying to stare at Waiting On Party Members for a few minutes, especially since I'm always the HM's healer or tank, but I don't feel entitled enough to get uppity about it.
However, there have been a few cases where my "could we please spacebar?" was met with outright hostility. Those people I sometimes conveniently forget to heal or pull agro off of them, I admit. :P
It's just so silly to me that there is this big divide of hate between spacers and watchers. I mean, really. I loved watching them the first time (or first dozen times) too, and I really don't mind at all if people actually communicate and say they'd prefer to watch. But usually the request is responded to condescendingly or, more often, simply ignored.
I try to run at least one HM a day, often two if I get both my mains in, and I have to say that the watchers are far outnumbered by the spacers in my experience. By that I mean it's almost always 3 people asking for skips and 1 person sitting silent. Doesn't mean watchers are in the wrong, but it does indicate (to me) that a group of people in rakata/black hole gear are probably there for comms and not cutscenes. Neither is right or wrong, but why not be considerate?