"In my opinion" is not a magic phrase that you can use to say whatever you want. Opinions are subjective evaluations of things for which there is no justifiable

"In my opinion" is not a magic phrase that you can use to say whatever you want. Opinions are subjective evaluations of things for which there is no justifiable objective answer, such as personal preferences and judgements. Saying that the sky is green is not a valid opinion, because the sky is not green, and it can be shown not to be so. Some things are not a matter of opinion.