I hadn't a clue that performing in blackface was still a thing, but some part of me knew that if anyone in the United States still performed in this shall we say "controversial" medium it would probably be a cop. Now the whole country knows that, yes, blackface is still a thing some people do and yes, the master of the art form is an ex-cop who was fired from the Baltimore PD for being too racist. Pause for a moment to consider how racist you have to be in order to be ruled Too Racist to be a Baltimore police officer.
Assuming you are not performing in a film or play in which re-creating the late 19th or early 20th Centuries involves the realistic depiction of a minstrel show, it is not complicated to determine whether or not donning blackface is a good idea. For anyone who might be confused I have assembled a handy flowchart. Consult it as often as necessary.
The academic part of me thinks I understand, or am capable of understanding, why people behave the way they do. I'm no sociologist or psychologist, but it doesn't take much to come up with a persuasive explanation of why people think this sort of thing is OK. At the most basic level, though, I have a difficult time fathoming how an adult human being would need to have it explained to him – in 2015 – that performing in blackface maybe isn't a great idea in the midst of a racially charged series of events involving the deaths of black men at the hands of cops.
Can anyone's lack of self-awareness be that complete? Or does he know but simply loves to troll? Given that the stated purpose of the event was to raise money for the indicted cops, trolling seems unlikely. That only leaves one option.