Selfish mining attacks are possible with any PoW cryptocurrency even Bitcoin. It isn't something unique to Monero.

If you voluntarily use a crypto that has inflation, no it isn't theft. No one forced anyone to use Monero. Gold mining isn't "theft" because more is mined every year. That would be ridiculous.

Monero/gold mining is open to anyone, requires PoW, and is predictable
Fiat inflation is closed to a select few, requires no work, and unpredictable

To say those are the same thing is dishonest

Any "fixed/predetermined" block reward or supply is only as good as the users that are in consensus with those rules. Code cant control people choosing to leave or join the Bitcoin network and taking their money with them.