Maybe you should have been more clear? You just said it became "unusable" which is not the same as "screen becomes unusable" - to echo you, go back and read what you wrote. From the lack of information, I had to assume you meant a charging problem since you did not really impart any useable info and really the only thing a charger SHOULD affect is the charge. If plugging in to a charger affects the SCREEN, which is what you now appear to be saying, all I can say is that is truly weird since 5 volts DC is 5 volts DC regardless of source. Unless something is goofing up whatever weirdness Moto is using to detect docking somehow which, really, they probably should not be doing since it likely breaks the USB standard.
And, hey - YOU generalized, implying that all Motos fail when you plug generic chargers into them. That is not the case. To quote - "while if you try and charge a moto with a generic charger it becomes basically unusable while its charging ." Nope. Yours, yes. I accept that there is something wrong with your phone or possibly your generic charger. The correct phrasing would have been - "It's not unheard of for a Moto phone to fail to operate correctly when connected to a non-Moto charger." So as long as we are correcting others here, I returned the favor. You're welcome.