First, it's not a true charity either, since the patron does receive value from it: a status boost.
Second, it's still a patronage relationship, so the principle applies.
Let's conduct a little mental experiment: Michelangelo starts consuming funny shrooms recently imported by sea, and abruptly switches his genre to crustacean porn
(look up "lobsta girl" sometimes, with brain bleach within easy reach, of course).
Since it's not early XXI century USA at all, this gonna cause trouble. Including loss of face for the Patron of Arts, through no fault of his.
If the patron noticed this before too late, what we could expect in this situation? Assuming we have a good idea of the era (via books like The Machiavellians
by James Burnham or History of Florence
by Niccolo Machiavelli himself).
Most likely, the patron's men would gently abduct Michelangelo and quietly move him to some village far from foreign hallucinogenic substances and painting supplies for a while. The unfinished "innovative" work would accidentally catch fire, fortunately put out before anything else is damaged.