Opinions are not backed up by fact
By definition, an opinion has no facts to support it.
Have you ever read Mark Twain? I have a lot, but I'll refrain from sharing one of his Twainisms - one which is most appropriate in this case.
P.S. Edit (because I'm here to help) One can certainly consider a fact, or any number of facts, while forming an opinion. But the fact is, people are entitled to form different opinions; but those same people are never entitled to their own facts. Facts are universal. Opinions are personal. And all too often around here, people confuse the two.