A lot of times in life, whether or not you should do something has nothing to do with whether or not you can get away with it legally. Unfortunately, this is something the selfish and self-entitled narcissists of the world fail to understand.
It’s surprising that you’d have to tell anyone this, to be honest. But, when someone leaves you to inherit a treasured family heirloom because they think that you’re the most likely person to enjoy it, treasure it, and respect it, the general expectation of that person and the family at large would be that you wouldn’t just turn around and sell that thing for a quick buck just because it’s the most convenient thing for you to do at the time. Imagine King Arthur hocking Excalibur off just because he was tired of lugging it around.