Why would a site need shills to make money? They poker sites take rake out of pots to generate revenue. The more pots played, the more money they make. The ideal situation for them is for players to play as much as possible.
Please also consider this argument, which is completely parallel to your own:
How can you prove that some websites aren't scamming?
You are a complete retard if you let them scam you.
I have no problem with banning websites worldwide.
I judge a religion as being good or bad based on whether its adherents become better people as a result of practicing it. - Joe Mullally, computer salesman