If the four-legged animal has fur, long whiskers, eats mice, and it miaows, it's perfectly reasonable to suspect very strongly indeed that it's a cat.

However, it is still completely unacceptable for it to be tortured into vomiting up the mouse-bones in order to prove it's a cat.

Likewise, it's perfectly reasonable to suspect very strongly indeed that people who (allegedly) behave like terrorists-in-training are, in fact, likely to commit terrorist acts. Not only reasonable, but very prudent.

However, it's still completely unacceptable for them to be tortured into admitting their intentions (or their past offences).