As you pointed out, every single poster on this thread has already figured out that this "study" is nothing but liberal propaganda.
Murray Strauss is not really a "researcher." He is a campaigner to change the laws so that parents will be arrested for spanking their children, as is already happening in Europe. (Of course they're not having many kids over there and those nations are quickly dying out.)
He's like PETA except focused on families instead of animals. Do you think that PETA is going to release a study that says that eating meat is good for you? That will happen before Murray Strauss will release an honest and unbiased study on the effects of spanking children.
Every couple years he comes out with some similar B.S. study, all of which are similarly biased and based on pre-determined conclusions.