In Edward Bloor's book Tangerine, why do Paul's parents ignore Erik's cruelty?

The Fishers ignore Erik’s cruelty because Erik is a master manipulator who is easily able to mask his true self when his parents are around him. He quickly morphs into a sweet, innocent boy when the Fishers are around, but he cruelly turns on Paul as soon as they leave the room. It helps that Erik often has lackeys, like Arthur Bauer, do his dirty work, so most of his cruelty cannot be traced directly back to him.
The Fishers also ignore Erik’s cruelty because they are willfully blind. Edward Bloor stresses that the Fishers, particularly Mr. Fisher, are captured by a strange phenomenon, the “Erik Fisher Football Dream.” Mr. Fisher wants Erik to play Division I football and lay the groundwork for a career in the NFL. Mrs. Fisher seems less enthusiastic about this prospect, but willfully supports her husband’s mania. Consequently, anything that might tarnish Erik’s reputation is pushed into the background. Anything that contradicts the Erik Fisher Dream simply does not exist.
Through this characterization of the Fishers, Edward Bloor may be criticizing our society’s tendency to lionize famous athletic stars and forgive them for any transgression, especially compared to a regular person who commits the same crime or has the same moral failing.