Of course, Toadwoman was right there on the spot, ready to leap on any mistakes Hagrid made. Hagrid took her faux-deafness at face value, giving her an excuse to write him up as barely able to speak English, and with the help of the Slytherins, she was pretty easily able to portray him as dim, disturbed and dangerous. Of course he's dangerous! Magic is dangerous! Take a look at Quidditch, for Merlin's sake! Or Potions class, where explosions and melted cauldrons are common occurrences! But our darling High Inquisitor had her own little axe to grind, and grind it she did, to the point that Hagrid's job hung by a thread.