You have a right to free speech. But you can’t yell “Fire!” in a crowded theater (unless there actually is one). You have a right to freely exercise your religion. But if your religion requires you to kill those who are unwilling to convert, you cannot exercise it in that respect.
Yes, the government has a right to constrain your exercise of certain rights. The question is whether or not Sen. Obama supports constraints that have an objective other than keeping you from bringing immediate harm to someone else.
The issue is that he uses variations on “reasonable regulations”, which while sounding like something we can all agree on, really mean something radically different to different people. Our side almost never calls the other on what they mean by “reasonable”, never asking what principles lead to such regulations.