Well, your tone and language were authoritative. Typically, if you aren't stating a fact you should qualify it with something like "I think".

Regardless of my tone. How can this be anything other than my opinion? Isn't it obvious that it is my opinion?

No, that's why I asked. You were stating something in direct contradiction with the article, and (going purely on prior) you probably haven't actually used a WP7 phone, so the implication was that you had more than opinion behind your comment.