Don't shake babies or kick volleyballs:

 

When our boys were growing up, our family's one-liner for categories of behaviors that were off limits was, "You don't shake babies and you don't kick volleyballs."  It was self-explanatory, it was easily understood, immediately comprehended, basically it was simple and to the point.    

Life consists of many choices contemplating: can you versus should you?  Mature people know how to distinguish between what is allowable and what is appropriate.  

There are commonsense subjects that normal people do not make fun of or celebrate, and when these values, mores, and norms are violated, there are social and cultural consequences.  We can ask who defines hate speed, are we defending free speech, and can we argue publicly over any issues we want? but we also know there are times when respect should triumph over political division and politeness over polarization.