Male facere qui vult numquam non causam invenit.
(Publilius Syrus, Sententia 336)

pron = MAH-lay FAH-keh-reh kwee woolt NOOM-kwahm nohn KOW-sahm in-VEH-nit.

The one who wishes to do evil is never without a reason to do so.

Comment: We can probably give evil-doers a little bit of a break on this one. The fact is, anyone who has made up his/her mind to do a thing will not be without "reason" to do it.

Best to look out for these folks, and get out of their way. I always start looking for them in the mirror!