Well, you CAN make an induction generator- but you have to have an excitation voltage present to make it work. In fact, if you take an ordinary induction motor and instead of having it drive a load, drive it FASTER than it "wants" to turn (ie, faster than its synchronous speed), it will in fact generate power and feed it back onto the supply grid. It just can't start from scratch, you have to put it on an AC grid to generate the induced currents in the armature before it can start generating. And, if you do this on a large scale as wind-power "farms" do, then you need to pay attention to things like power factor correction (relative phase between current and voltage) because induction motors and generators don't operate at unity power factor.
But yeah, I agree that saying "every motor will act as a generator" without caveat is incorrect. If you want to use, say, a variable-frequency drive AC motor as a regenerative brake, its got to have a "smart" controller to make everything work right. Not the least part of which is deciding when to start applying the friction brakes smoothly and seamlessly so the driver gets however much stopping force he wants without noticing a change from regenerative braking to friction braking.