So my question is, without anyone defining "rules" up front in a PuG, was I out of line?
A bit from Column A and a bit from Column B.
I play at odd hours so I do a lot
of PuG flashpoints and I can't remember the last time someone asked at any point to define loot rules. It's pretty much universally understood that Need is for stuff that goes on your back exclusively. Companion loot is greeded unless you really have the hots for a piece, then you ask first, in which case I've never heard a team say no.
On the other hand, kicking you over what most people would consider a relatively minor looting faux pas
is a trollish move. I've seen newbs Need on the wrong gear a few times and they generally get a mind scolding about proper etiquette.