Laying the censorship issue to the side for a moment (I'll come back to it), the ratings boards could fit either model of parenting, both responsible or irresponsible. However, the question you should ask is whether the ESRB and the like should be done away with because some parents will use it inappropriately. Should we get rid of genre designations in the local library because some parent may decide that anything that looks "cartoony" must be okay for kids? To reverse the question, should responsible parents be forced to deal with the morass of entertainment and media options for their children? Is it going to do more good or more harm to remove this tool?
Returning to this idea that ratings are a form of censorship, I must point out that ESRB rating do not, I repeat, do not effect whether or not you can write a game. Assuming you have the means (a computer and familiarity with a programming language) you can write anything you like. However, the simple fact of the matter is that, for the most part, entertainment is a business venture. Businesses that take on the expense of publishing games want to see those games sold to the largest audience possible. PG-13 movies regularly out-earn movies that are rated R (http://www.allbusiness.com/services/amusement-recreation-services/4729717-1.html); this just makes sense, as more teens and families are likely to go to a PG-13 show. Writing an edgy or controversial game does not fit the format of maximizing earnings. You can write it. But no business is required to sell it. And no consumer is required to buy it. That's just the way the market works.