it is their money and they should be free to spend it anyway the bitcoin protocol allows.
Of course, but they try to do something in an incorrect manner thinking that they're correct. You don't burn coins if you send them to any valid bitcoin address, you may trap them, but you don't burn them.
The transaction fee was meant to pay for storage in the utxo set.
And that's why an OP_RETURN transaction costs less than a "trapping" transaction.
The worst thing is when people try and say "dont do this and dont do that because it's bad for bitcoin" when bitcoin itself allows it.
Yes, it's personal responsibility after all. If a few more users mixed bitcoin, you have no idea how more difficult it'd be for chain analysis companies to trace the chain, and therefore how better it'd be for bitcoin privacy-wise. Bitcoin itself allows even more things, it doesn't mean you should do them.
not a big fan of op_return since "Many members of the Bitcoin community believe that use of OP_RETURN is irresponsible in part because Bitcoin was intended to provide a record for financial transactions, not a record for arbitrary data"
Actually, that's the very reason you should be a fan of OP_RETURN, because those who would have the intention to store arbitrary data would do it either way, in an inefficient way, bloating the set with unnecessary outputs such as in
this case.