The Brief: "Read for filth" means to harshly criticize someone to the furthest extent.

Bluesquiggle
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“Read for filth,” sometimes quoted as “read to filth,” is a popular phrase meaning to harshly call someone out or lay into them.  The phrase is normally used in a humorous manner.

According to Urban Dictionary, the phrase traces back to July 2016, but as of June 2020, it is seeing a resurgence in popular slang IRL and on the internet, most notably Twitter.