Yeah, opinions can be wrong.
Edit: Actually, to be more specific, opinions are neither right nor wrong, but many people use the word 'opinion' to mean 'qualitative fact without an easily identifiable answer/answer that I don't personally understand.'
"MK is my favorite alliance" is an opinion. "MK is the most politically significant alliance that is no longer extant" is not an opinion, it's an ill-defined fact. The first cannot be right or wrong, the latter can.