"I disagree with PersonX's opinion." - a simple statement.
"PersonX's opinion is wrong and PersonX doesn't know what's good." - An attack on someone's opinion.
An opinion, by definition, cannot be "wrong" or "right". It's the nature of an opinion. Now, an opinion can be ill-conceived, if it's based off of poor information. An example would be something like "I think it's wrong to do that because it's illegal." when there's no such law that says it's illegal - the opinion isn't right or wrong, but the basis for forming the opinion is faulty.
In this case, his opinion is, basically, "This show is terrible because it's a comedy and I don't find it funny."*
You say he is wrong because he doesn't know what is funny. Since comedy is subjective, you can't really say if his opinion is based on faulty information - any more than I could split a group of people into those who like fake watermelon flavoring and those who don't like it, then tell one of the groups that they're wrong and they don't know what's yummy. You can't *know* something that's subjective, and to suggest otherwise is an insult ("You're too stupid to know what's good." - or, basically, "You're too stupid to not have the exact same subjective opinion that I do.")
*Another example of an opinion based off faulty information would be "Man, Shindler's List is a terrible movie. It's the most unfunny comedy ever."