Guilty or not, his actions, all of our actions, will usually be under a magnifying glass. It totally sucks, but we have to keep our noses cleaner than the general population. If a plumber had killed that dog, nobody would make assumptions about plumbers. But when a Marine or sailor (or soldier/airman) does it - then it brings undue (and COMPLETELY unjustified) derision on his or her respective organization.
What happened to MB is, based on my experience, an example of a skipper taking the easy way out. MB was accused of a crime that reflects VERY badly on the US military, officers in particular, and one that there's ever more pressure to handle expediently and harshly. That kind of crime brings unpleasant attention to a command. A skipper who does not care about his guys may see it as easier to just kick the officer to the curb rather than stand up for his guy and bring yet more attention to his command.
Bottom line - we're held to a higher standard and even accusation is enough to end a career. We are tried by a jury of everybody and if we even appear bring discredit on the military, you can bet that more often than not, you're going to get fried.