Only reason I can see for not pulling the whole room is that you *couldn't* handle it easily. And there's only two reasons you couldn't handle it easily, either gear or skill. Since it's not your gear, hopefully the group you left got in a skilled tank to replace you.
It's also worth noting that since pre-formed groups missing 1 member move to the head of the line, you're petty attitude of "I'm taking my ball and going home" has *very little* impact on the groups you leave. Probably MOST of them are saying "I'm glad he's gone, what a ****!", then select replace member and welcome him with stories about the douche he's replacing.
This is a thread about why tanks aren't in the LFG q, but you illustrate very well why many dps are willing to pay 30g a run to group with a non-douche tank.