Let's simplify this:
You have children, do you deny them anything that they need? No. You provide for all their needs.
Yet one day, while all their needs are met, they go ahead and stick their little hands into the cookie jar even after you have told them no.
As the cookies were not theirs to begin with, nor were they something in which they were given, I do not see the tithe as being applicable here.
Yes, they took that which was not theirs to take.
Just my 2 cents.