You can't just say something is incorrect without elaborating on why. Because then it just comes off as you saying "you're wrong because I say so."
Sure. I don't expect to convince you. You've long stood by your position. You don't feel the obligation. It's your position, but that's all it is.
Very simply, people who participate in charity have superior societies than to people that don't. Same with people who choose certain forms of collective governance. It's obviously possible to have too much charity. It's also possible to have too little government or too much. In the long-run, the fact that the universe is deterministic will show that your behaviour merely free-rides off of the correct choices of others. Your choice was not the correct choice, because it's not replicable. If I act like you, we can wait for a few more cycles, and it turns out that everyone is worse off than if I didn't. Both me and you. Whereas, if you change, you (and yours) are better off.
Additionally, it's also contained within the definition of 'obligation'. It's a moral onus. The moral onus exists within its definition. It is, by definition, "good" to be charitable. It is, by definition, 'circular' to have no angles within the line. If someone says that their square is circular, and who am I to disagree, they're just being nonsensical.
It's akin to someone insisting that overeating bacon is healthy, and then quibbling about what the word 'healthy' means. "I like it, and I don't mind having cardiovascular issues later, and thus it's healthy" is their argument. Sure. But, they're wrong. And they're just wrong cuz they're wrong. They're just using the wrong word.
No. I would argue there is a moral imperative about solidarity, but there is not about charity.
There is certainly a practical imperative towards solidarity. The family that saves the kids when the house is on fire will do better than the family who ignores the kids because they can carry more of the pets.
But if I see someone drop a twenty while they're walking, there is no ethicist on earth that says that I should watch the bill fall, scoop it up, and put it into my kid's educational fund.
Everyone, even Commodore, knows I should inform them that their twenty is on the ground behind them.