I agree 100%. But I don't think that this increase in the levels of 'vitriol and poison' is a national trait - instead it is something that started to occur and has grown steadily since the year 20 PMP
* and it is getting worse as the years and technology roll by.
I've always been amazed by how many times a text message (which was originally meant to be light-hearted or joking) so often can get totally misinterpreted. The reason for this, I think, is purely because texts have no 'tone of voice' - in other words, a text is always cold and impersonal. And putting even putting a

or umpteen :-) :-) :-) :-) :-) after a message doesn't add up to real smile or a belly laugh in a conversation.
Instead, a text or message on Social Media will certainly come out colder than saying the very same thing to someone face to face - and that is mainly because, when talking face to face, the recipient can easily listen your tone of voice, see your facial expression, respond to you body language etc. but with a text you can't do any of that.
Even saying 'I love you' in a text message comes out as far less loving than it was meant by the sender. So, it follows that saying something nasty in a text message comes out sounding far nastier too.
Sadly, there is even worse to come. Social Media messages have inherited all of that 'coolness' and 'impersonal-ness' of phone texts but added two seriously toxic elements - Anonymity and Invisibility.
These two additions make it even more likely (ie makes it dead certain) that some dim troll-ish people out there will go to town on the offensiveness with absolutely no fear of any repercussions and no restraint.
And it is
this which is wearing away at our good old British politeness and reserve. In short, our famous stiff upper lip is being replaced by the trolls' and their famous stiff upper heads. Then when you get several trolls responding one after the other then escalation soon gets to napalm levels.
Worst of all, the trolls' grammar is bleedin' terrible! And it's getting worse. I dread to think where things will all end up in another ten or twenty or fifty years from now given the sheer speed of techno advances over the last ten years or so - maybe with mass burnings of the OED on every street corner? Followed by a virtual lynching or two?
PSP
* = Post Mobile Phones.