From the beginning, Marcel stood apart from the other contestants. I don't think it's due his lack of social skill, because if you look at each contestants, I don't think any one of them set an example for social grace. I took notice of Marcel in the first episode when I learned he works at a Joel Robuchon restaurant. Joel Robuchon trained who's who of top chefs, and is considered one of the best, if not the best, chefs in the world right now. Compare that to other contestants--caterers, line cooks, room service cook. Sam and Cliff may be executive chefs, but not at very well known restaurants.
Now, for Marcel's social skills, he works at a very large kitchen, probably works with more people than the other contestants do at their workplace, and guessing by the clips from the last show, he lives with several other chefs. I don't think if he truly lacks social skills, he could survive in that environment.
I think other contestants decided to disliked Marcel, and interpret he's words and actions in the worst light. I liked Sam and Ilan at the beginning, but now I think Marcel deserves to win for putting up with all the immature unprofessional behaviors without whinig about them.