The funny thing is there's no explanation for why exactly the black hole started blasting radiation at innocent passers-by.
It all started when the Red Dwarf (Brug) made eyes at the White Giant's (Hoopy) girl friend, a comet who was not as innocent as you may think.
So Hoopy bought the Acme Black Hole Radiator X35 - Platinum Edition (hey, the coyote wasn't making good use of it!) and turned the switch.
Thus did Hoopy get his revenge.
Never mind that he obliterated 17,512 systems in his immediate vicinity because he put the shielding on backwards but it was a small price to pay.
So it really wasn't all that innocent now, was it?