I don't think that he is wrong. Even if I did, I still wouldn't disobey him.
The muggles at home think that magic is caused by demons and devils and if they have magical children then they punish them. For accidental magic. It's cruel. If they knew I was a wizard, they'd hurt me, or they'd try to conduct terrible experiments on me.
I haven't heard of Professor Egg. Is his book awfully dull? Perhaps I'll read it, if I find it.