to blast (someone) on the chat app; to criticize, - shame


Explanation:
Not a new term meaning to criticize heavily :

http://www.oxforddictionaries.com/fr/definition/anglais/blas...

informal Criticize fiercely:
the school was blasted by government inspectors
Autres phrases d'exemple
She has blasted the senator's criticism of the war by reminding viewers that he voted for the war.
Critics blasted him for pouring taxpayer funds into badly managed banks and unneeded infrastructure projects.
It was also a colossal failure, shunned by audiences and blasted by critics as ‘pretentious.’

Or to shame someone :
http://fr.urbandictionary.com/define.php?term=blast


You could probably go with a synonym to fit your sentence more smoothly :

He told you to stop putting people down [...], SG (just like you asked him not to do it [...] either, JP), he souldn't have reacted like that!

"to put (someone) down" might work well.