Why? It's presented as a dictation exercise of a conversation between 2 people talking about historical events. Probably very few would disagree with anything they are saying, but it shouldn't preclude the first speaker from commencing one of her statements with "À mon avis".  I don't understand how that offends you so!

Only one side of a very volatile subject is presented. A mon avis, I would not call this "un acquis precieux" or "une victoire".

I simply gave my opinion. Thanks for your input.