Many people don't understand the difference between "genetic modification" and "selective breeding". The Cornish cross meat birds are selectively bred, IMO they've overdone it, but there's nothing inherently hazardous about it. It all chicken genes, mixed by breeding only.
They are NOT GM, that would involve gene splicing, a process that allows genetic material from not only the same species, but from whatever, to be inserted into the organism. Such as wheat genes in corn, fish genes in strawberries, spider genes in a goat, etc.
It is not an evil plot by the "anti-establishment crowd", (which is just another false label to try to discredit anybody who might question the status quo of anything) to discredit the establishment, but merely ignorance of the subject. People who question the status quo come from all backgrounds, and have opinions anywhere from far right to far left, so much so that the label is meaningless. You might as well say "the type 'O' blood group crowd", as if they all thought exactly alike.