He said that review, not the entire site.Well Gamespot gave Super Mario Galaxy 2 a perfect score of 10, so that disproves your claim that they have a bias against Nintendo.
Djinn's right though, assuming they are trying to troll with this you're giving them exactly what they want. Any form of upset at them for this is problematic in its entirety, I'll explain why:
1. If they're being entirely honest, then they have their opinion and outrage is wildly inappropriate because that indicates that it's an injustice for someone to dislike something you like. Disagreements in terms of taste are a given; they're always going to happen no matter what and getting upset about it will only cause yourself unnecessary and fruitless stress.
2. If they're trolling, then regardless of how negative your attention towards them is, it's still attention; it's free publicity. Your outrage is misplaced because it ultimately is exactly what they're looking for.
It's just a negative review. Every game is going to get at least one. Don't be too upset about it.