I am moderately thick-skinned to what is posted on the boards, so I look at intent as much as wording. For instance, on the general boards, there is a person who uses "escort" in posts that are very misogynistic with the intent to troll. Normally I don't think of "escort" as an insult, but when that guy(?) uses it, it definitely is.
Before I began my foray into this world, I read the boards quite a bit, and I was shocked at the use of hooker, but I've since come to realize that some don't think of it as derogatory. However, because of the negative connotation, if one chooses to use words like that, they ought to be aware that they will offend some, especially when it's obvious that a few men (not all) have a very negative view of the women who are here or women in general. I'd like to think the gentlemen who indulge in the hobby are simply sex-positive explorers, but it's clear that some have nothing but contempt for ladies while partaking in their delights.
I use companion on my website. While nothing is wrong with a quick roll in the hay, my personal preference is for something more, so my word choice hopefully conveys that. Maybe it's because a tiny part of me is still old-fashioned, but I like to have some level of mutual respect and mental attraction to those I meet. I also think of what I do in a very positive manner even if that is counter to societal attitudes.
As for what isn't generally offensive, provider, companion, escort, and working girl are probably the most acceptable, but the rest of what is said matters, too.