If you disagree with someone enough to feel it’s necessary to say so, it’s generally advisable to explain exactly what you disagree with and provide reasoning for your stance. Otherwise, you’re just making noise. A truly informed person has no trouble coming up with a few examples to back up their claims. It’s quite patronizing to imply that you have some insight I don’t, and then not even bother to share it - especially when following it up with, 'I don’t think we can agree,' after putting zero effort into reaching an understanding.