Many, many groups besides Muslims have training camps for "terrorists/insurgents/freedom fighters/guerilla fighers", etc. Whether or not the governments of countries like the US recognize them as "terrorists" really depends on whether or not the US is using them to further their own agendas. Often, when the US is using these people as proxy fighters, the government of the US refers to them as "freedom fighters" or as "rebels". The only thing that determines whether or not they will be labeled as "terrorists" is whether or not they are useful to the US government.

In the case of Muslims, at this point in time, the US government's agenda is better served by calling Muslims terrorists rather than any of the other names they could be using. Back when the US was using Muslims in Afghanistan as proxy fighters against the Soviet Union, the government of the US had other, more benign names for them. And of course, many of those very same people, trained by the US in Afghanistan, and doing the bidding of the US there (Osama bin Laden being the most well know of these), are now considered "terrorists". It's all the same thing, though. Just different spin.