Wow, someone who still things mens rea means a damn!
In far too many cases, simply 'causing alarm' is sufficient.
Example: In most states, openly carrying a firearm on your hip is legal. Depending on the area there are often restrictions as to where you can carry (bars, schools, playgrounds, etc) and what limitations private businesses can put on your carrying ("We prefer that patrons not carry firearms here so we must ask that you leave now, if you refuse we will ask the police to charge you with trespass" vs "Seems you missed our legally binding 'gun free zone' sign... guess what? you just committed a crime! Please wait here while the police come to arrest you").
It seems cut and dry, until enough people freak out that someone is carrying a gun and suddenly you can be facing charges despite acting fully within your rights.