You must be new here. ;^)
Lately anyone who is against nation-building, perpetual war, the Patriot Act, etc. are considered leftists. There's even an ongoing attempt to get people who don't join the "Pro-War/Powerful FedGov" bandwagon banned from this site.
True. Although I disagree somewhat with Paul on Iraq (I think that once we invaded, we obtained a moral responsibility to do the best we can to stabilize the country), it is indeed bizarre that non-interventionism is now seen by many as a leftist cause. I suppose that is really as a result of Vietnam, which leftist radicals opposed for ideological reasons (they wanted the commies to win). Prior to that, non-interventionism was always seen as a rightist cause.