He loses all credibility because he don't like you religio.. I mean language? Strange metrics of credibility. I disagree with you, therefore you have no credibility.
You misrepresented my point. C# is far from my favorite language. He loses credibility however by making a statement which would appear wrong to any person with some knowledge of the programming language panorama. It's a red flag to either ignorance or intellectual dishonesty. Note that he didn't say, "C# is a language I don't like" or even "I find C# to be a horrible language", which would have been perfectly reasonable stances.