Nail on the head. You have a right to hold the opinion that Jack Morris was a better pitcher than Bert Blyleven. But your opinion would be wrong, because Morris was not a better pitcher. Blyleven was.
Now, if you want to say you enjoyed watching Morris pitch more than you enjoyed watching Blyleven, that’s also your opinion. Provided you are telling the truth, however, that’s an opinion which can’t be refuted by facts. If you liked watching Morris pitch more, then you liked watching Morris pitch more. But that would be a matter of personal taste, and not a matter of objective analysis. One runs into big problems when personal taste and objective analysis are confused.
I don’t think this opinion problem is limited to just baseball, by the way. There seems to be society wide issue with confusing subjective opinion and objective facts. Everyone has the right to an opinion; not everyone’s opinion is right.