I have noticed this. Messi and Ronaldo are both great players, and they have their own strengths and weaknesses. In order to become a Messi fan, you don't need to hate Ronaldo (and vice versa). And I don't think that there is any personal hatred between these two players. The fans need to understand that. All that said, IMO Messi fans who hate Ronaldo are more common than the other way around. And what would be the reason for this? Nothing comes to my mind right now.
Of course being a Messi fan doesn't mean we should hate the Ronaldo just because of the rivalry between them. The rivalry between them is what motivated them both to keep pushing themselves to the extreme and it is not as if they hated themselves the way the fans are taking it. They are both great players that we should appreciate and seeing them play in the same era is a blessing because I don't think there has been any rivalry as intense and competitive as this one.
I have asked a few Messi fans i know and their answers for hating Ronaldo is ridiculous, they all claim that he is arrogant and that is their reason for not liking him. I don't believe them though.
Those who blame Cristiano Ronaldo whenever Al Nassr suffers defeats are mostly people with very low knowledge about football or Lionel Messi fans who are always looking for the slightest opportunity to criticize the Portuguese-born football superstar. How do you criticize a striker who is delivering his job which is to score goals because the team defenders failed to do their job which is to defend the team from conceding. At age 40, Cristiano Ronaldo is still scoring goals than most of the young strikers in world football. You just have to respect him and his incredible achievements
You're right, most critics comes from Messi fans looking for an opportunity to criticize Ronaldo that's why they expect Al Nassr to never lose a match. He is not responsible for other players performance and when the losses it shouldn't be in him. Had it been he is not scoring goals then it is okay to criticize him but he is even scoring more than any player in the league that means he is playing his part for the team.