Being offended is a personal choice. It's up to the individual if they feel offended or not. You're talking about feelings here, no inciting violence or hatred or making someone feel threatened.
Boris didn't make anyone feel threatened did he? Or the guy with the pug. No, they hurt some people's feelings.
Absolutely, if we concentrated on politeness, maybe teach tolerance more strongly at schools then we can break some of this cycle. Freedom comes with idiots am afraid but I'd rather encounter idiots than have any thoughts quashed by the law.
We can also teach tolerance everywhere, including some tolerance when idiots say idiotic things, instead of being offended or, in the case where it does not directly affect us, be offended on behalf of others as seems to be the trend now.