The UN have designated some Uyghur groups as terrorists, and these groups came into contact with Islamic fundamentalists in other regions when China relaxed travel restrictions for a while, which allowed Muslims to make Hajj. Some of these groups have taken part in terrorist attacks within China.
That doesn't justify the measures taken by Beijing against the Uyghurs in general though, but that's China, where they don't do things by half. You could certainly argue the case for genocide but there are other Muslim groups in China, with about 120m Muslims in all, with the Uyghurs being the largest. Most of these are Sunni and the ones outside Xinjiang appear to be well integrated. As ever, it's never quite black and white.