If you had limited yourself to saying that you found the article difficult to believe, that would have been no problem.
If you had added that in the past Dawkins has not held that view that would also have been no problem.
If you had stated that you thought it was likely that the reporter had misrepresented Mr. Dawkins that also would not have been a problem.
But you went far beyond simply voicing your opinion. You made accusations and insisted that this was a dishonest, religiously motivated article and that it is propaganda.
You did not say that it was your opinion that the article was propaganda. You did not say that it was likely that Mr. Dawkins was used in a misleading and dishonest way.
Furthermore, if you produced a link to a statement made by Mr. Dawkins after that article was published in which Mr. Dawkins stated that he was misrepresented in that article, I would be persuaded and it would not be against my will.