This is odd because فيصل is not Lebanese and the show is not on a Lebanese channel, Lebanese very frequently use English or French words and expressions and sometimes complete sentences. Why did he used English? well, It might be to mitigate his guest's anger and emphasis that he has empathy with his opinion. I am suggesting this because when I am having a conversation with some of my close friends I usually try to use words or sentences form a foreign language that they know even if I don't speak that language well. However, if I am speaking to someone who doesn't know English, for instance, I never use English words that he/she would not understand... I guess that they consider it rude because it would seem like I am trying to show that they are lower of me because I know English and they don't or something like that.

The way he said it sounded as: [I'd say it even in english -you're doing very well-, but let me speak] It's like a conversation technique he had worked out to stumble the other person to stop talking and become more agreeing; diverting his attention by English, and conveying the meaning which was agreed to.

English language is quite wide-spread in Lebanon. The interviewer may have said it out of habit, or maybe to strengthen the fact that both of them can master English.

I have no answer to this to be honest! It does sound really odd to me to hear it like that on Aljazeera channel. You would hear Arabs speaking phrases in English sometimes, just to show off especially if the whole conversation was in Arabic and there was no space for English in it! The way Faisal Alqasim said it though, sounds like one of his tactics to cool his angry guest :)