I can't say that I agree with you on this one, Jalima, but life would be very boring if we all agreed with each other all of the time 
Personally, I think that the discomfort we feel when first hearing Mary's choice of language comes largely from the fact that it isn't what we are used to on factual TV programmes. I don't mind admitting that it gave me food for thought initially, but I quickly realized that I wouldn't bat an eyelid at that kind of presentation in any other format, such as a university lecture, so why should I care if it's on TV?
As for it "putting off a lot of other viewers in the process", well yes, perhaps, but I'm sure that there are still plenty (the vast majority?) of other programmes out there on a similar topic that will not offend their linguistic senses.