By which he seems to mean, ads that he personally doesn't approve of. More specifically, he's afraid that the fear of ads against Democratic candidates have stopped them from raising your taxes as much as Mr Willard would like.
He's also not too keen on anyone criticizing politicians, unless a) they are criticizing Republicans, or b) are members in good standing of the priestly MSM caste:
“ Stop making the false argument that a ban on negative campaigning is an infringement upon free speech.
Well, one man's mudslinging is another man's “ speaking truth to power”. Mr. Willard goes on:
“ Here's another idea: Ban third-party committees that run negative ads.