I would agree that being poly does not catapult you into the highest risk group. Being irresponsible does.
Also, I really have a pet peeve when people keep calling polyamory a "lifestyle". Lifestyle suggests that poly people dress a certain way, buy the same things, follow the same entertainment and politics, etc. To me, it's a way of structuring relationships not a "lifestyle".
It's kind of like saying "the monogamous lifestyle". It comes with a ton of assumptions that really don't apply to the vast diversity of people who identify in that group.