This is the negative uphill battle Snyder faces, especially with the critics. We have also gotten to the point where unnamed, unverifiable sources can literally say anything and the people treat it as fact. They said the same things about Wonder Woman too. If JL is a success, they'll give credit to Whedon. If it's deemed a failure, all the blame with go on Snyder.
You can only give an artists so many chances before you stop believing they can deliver something that works for you. If JL is a failure, yes, unfortunately for Snyder he's going to cop it even if he has been held on a leash, but you can't say he didn't play a major part in generating the negative build up.