If he wants to be a spendthrift then he should be doing it on his own dime, not being subsidized by everyone else in the household. Or does everyone else not notice or care that he's throwing out sponges that could be rinsed off in like 5 seconds and then be ready to go again?
To be fair, those were soaked in stove grease, not just dirty. I don't think there's any malice on anyone's part, just three different ideas of how a house runs being combined. Like my other roommate never used a dish drain, so she keeps putting dirty dishes into it.
Hail to the Lord of Death and Destruction! CATNIP FOR THE CAT GOD! YARN FOR THE YARN THRONE! MILK FOR THE MILK BOWL!