Amp wiring question is it safe to run 4 speaker off one channel?

So i have a 2 channel amp kenwoood kac-7201 i installed it in my car yesterday and afterward my mechanic said its dangerous to install it that way i just wannna check to see if this correct because i think its perfectly fine but anyways. i have the amp bridged and wired to run 4 speakers at 4 ohms. the amp is bridged and is running 4 speakers at 4 ohms like the speakers specs states.but the thing im worried about is it safe to run 4 speaker off one channel?