You're bang on! 👏
I'm an NRI myself, and though I've always lived here, I see other people that have just come from India and completely adapted to their new surroundings. And clearly, Anupam had done just that - it's only natural for him to change a bit.
There was no reason for everyone to gang up on him. I didn't think he'd ever done anything un-Hindustani; most of the time, he spoke Hindi, and very well too. And I hadn't heard him say anything against India either. I appreciate that a lot of what goes on is off camera or may be edited out, but he's evidently not being different on and off screen, because none of the others suggested that.
As for the Shoaib issue...what was she expecting him to say? It's her Swayamwar, her dulhe, and her decision. If anything, I think Anupam had been quite mature in the way that he just let things be. He knew that she'd realise eventually, and that if he tried interfering, things were just bound to get sour between him, Ratan and Shoaib.
In all fairness, Anupam didn't help himself by getting stroppy when he and Ratan were talking. And I didn't agree with him when he said that there's no point of a relationship where you have to explain yourself. The way I see it, there are bound to be some misunderstandings, especially when they don't know each other that well yet. Having to talk to each other does not make a relationship "faltu."
But yes, he did have reason to get annoyed. Ratan was asking him such stupid questions! And he'd just been ganged up on for practially no reason.
Though he wasn't my favourite dulha, and though I don't think he'd actually have been the perfect match for Ratan, I do still feel that he was accused wrongfully, and that he was definitely misunderstood.