Blockchains are designed with abuse in mind. There's redundancy in decentralization that makes it effectively impossible to kill the network. Anything you can do is technically allowed. As long as you're not breaking laws, you can try anything you want on the network.
If the blockchain, dApp, or person you're targeting lets you do whatever you're trying to do, then no one's going to stop you.
That doesn't mean you're doing good.
Blockchain culture is too self-interested in my opinion. You have immense personal freedom, but you're still a member of a (largely anonymous) community. There's real people behind those public keys.
Just because other people will pursue profit through front running, sandwich attacks, and various other activities that directly harm other people, does not mean that's an ethical choice.
Code is law, but you shouldn't need a law to tell you to be a decent human being.
P.S. This thought came up in response to discussions in Discord about MEV and front running on Koinos. As a burn pool operator, I won't ever intentionally influence block production for my own personal gain. I see it as my responsibility to remain impartial on that front.