I'm not at all sure we could possibly pin a party political line to the black art of 'political correctness' here in the UK although it probably does have it's roots in 'liberalism.'
It is now a national sport and Twitter, it seems , is the vehicle of choice for those who are offended and want to let everyone else know how offended they are. The term "Twitter Storm" describes this electronically driven mass hysteria perfectly.
Where did it start? Pop culture has a lot to answer for when rap and hip hop stars routinely shot and killed each other for "disrespecting" them. Certainly, this trend has continued to grow and is now endemic in the younger generation. Dare to diss at your peril. It will cause great offence and may end in your premature death, a maiming at the very least.
It's a short step away from dissing, being dissed and being offended. Of course the main culprits of offence takers, at least those most publicised appear to be the vociferous wing of the Islamic religion. There, I've said it. They must have a "How to recognise two hundred offensive acts before breakfast" awareness handbook, as even farting in their general idiotic direction can bring about howls of protest and threats of ritual beheading.
THis is not a hate speech, (It is alleged), it is more of a dissemination of traditional stereotypical centre ground old white guy stuff.