Clearly, Toyota has the right to defend itself against shysters like Sikes. In fact, every automaker should have its own version of SMART in place -- not only to filter out bogus claims, but also to identify safety issues before they become PR fiascoes. Heck, if the SMART team had been around a couple of years ago, Toyota might've responded quicker to initial allegations and thus avoided many of its current troubles. (That said, Toyota is also obligated to provide a degree of transparency about complaints and investigations -- something it's not currently doing.)
Toyota should also be allowed to have its team of lobbyists on Capitol Hill. As long as politics and commerce remain closely intertwined (and as a recent Supreme Court ruling implies, that's the way things are going to be for a while), companies will have lobbyists. Its distraction campaign may be unseemly, but so far as we know, Toyota hasn't done anything illegal, and other lobbyists for other companies and NGOs are likely doing far worse. That doesn't mean we like the system or that we agree with the Supremes' ruling, but technically, Toyota is operating within the law.
Running smear campaigns against oversight groups and trial lawyers, however, is not such a great idea, and in fact, it could easily backfire. If the allegations against Ditlow and Kane are true, then yes, Toyota is within its rights to call them out; if untrue, however, this could result in some costly court proceedings for Toyota. And more importantly, attacking individuals rarely makes for good PR: at best, it makes companies look like whiners, and at worse, they come off like bullies. For a company trying to buff its image, neither is a great move.