The funny thing is that there are examples of both leftists using it to insult liberals and liberals using it to insult leftists: basically "you do not know hardship and that allows you to believe the inane things you do out of convenience."
It's like all arguments of this nature: there are liberals that are more comfortable with conservatives than leftists if they were just following procedures to do regressive things and there are leftists who use paper-thin progressivism as a shield against criticism and neither are representative.
But it was invented by two of the worst tankie, "ha ha dead Israelis and suffering libs are great", scumbags on Twitter. When they said "treatler" they meant libs. https://knowyourmeme.com/memes/treatler-treatlerite
Comments
https://knowyourmeme.com/memes/treatler-treatlerite
some treatlers are libs who call themselves the true progressives
most treatlers are reactionaries who call themselves whatever they think is the most self-righteous label to apply at any given time
the burrito fuhrer