While I agree with most of what he was saying, I think you are right. Strange admitted he could kill or banish Hulk if he wanted. He chose not to. The only reason he even ingested the demon was to proect himself in a weakened state, which happened because Strange made himself vulnerable in an attempt to reach out to Hulk. Even than, as Zom-strange he only failed to beat Hulk because he stopped himself. An unleashed Strange would own Hulk in two seconds.

If anyone on Earth could take out SBP it's probably Strange, although he's also as likely to lose to him given is weak vulnerability.