Many a Boston player have received standing ovations when returning on an opposing team. Hell, Boston threw Ray Bourque a friggin' parade after he won a cup with the Avs. Brady is such a unique case and how him and BB are linked, and people felt compelled to pick a side I guess. And that was mostly propelled by media as a whole, including social media, not just local. There's other factors too of course, like turning into a diva which never flies here. Talking to the Dolphins about his future while still on the Pats and allegedly mailing in that season didn't help his cause either. People definitely started turning on him before he left. Tom's dad predicted the breakup would be bad and he was spot on, and it spread into the fan base.
The Red Sox thing has happened on a few occasions for sure, can't argue that, most notably with Francona. They did him dirty.