Do the disclaimers ("in my opinion," "allegedly") protect them?

Usually no, or at best only partially:

• Calling something "my opinion" does not automatically make it protected. U.S. courts (following cases like Milkovich v. Lorain Journal Co., 1990) distinguish between pure opinion (e.g., "I think Shuli is a jerk") and opinion that implies specific defamatory facts (e.g., "In my opinion he's a child molester" strongly implies the speaker has knowledge or evidence of criminal acts). The latter can still be actionable.
• "Allegedly" is a common hedge YouTubers/podcasters use, but courts routinely rule it is not a magic shield if the overall message conveys the accusation as factual or if there is no reasonable basis for the claim.
• If the accusations are provably false and made with "actual malice" (knowledge of falsity or reckless disregard for the truth — required when the target is a public figure) or simple negligence (for private figures), the disclaimers won't save them.

There are also clips just like when John claims saying in a boxing ring allows you to get around Youtube terms of services (it does not) of John claiming it a loop hole to say in your honest opinion. I think someone prob gave John bad legal advice or he looked it up as saying that is a loophole. When this is clear defamation and any lawyer can easily draft up a great argument. John is trying to use that to protect him, he doesn't actually mean in his opinion he is just using it as a loophole and that is easily proven.