I'm not going into primary care. I am 99.99% certain that I will match in Anesthesiology this year as a soon-to-be Ross grad. I've had plenty of interviews side-by-side with U.S. students from a wide variety of allopathic and osteopathic schools. I've heard not a single negative comment, not from any fellow interviewee or from anyone I've interviewed with at any of the >10 programs I've interviewed at, nor do I believe the supposed "stigma" exists except in the recesses of the few small and incredibly insecure minds that populate these forums and/or the incredibly snobby, elitist programs that I'm really not, nor have I ever been, interested in training at.
Having said all of that, who's knocking primary care? First off, IM has the most sub-specialties offered, and many Ross (and other Caribbean) grads go on to fellowships. Still, who's knocking the primary care doc, the pediatrician, and the OB/Gyn anyway? Each provides a critical piece to the healthcare puzzle. And, I'll tell you what else, a FP doc will never - NEVER - be out of a job anywhere he/she wants to practice in the entire U.S.
So, worry less about stigma and what other people think, and more about getting into a good program, crushing your boards, and becoming the best physician you can. If you're going into medicine simply to satisfy your own ego needs, trust me - you've chosen the wrong profession.
-Skip