Not hard to tell

This always comes to mind when I see people acting like idiots online. It's from Tecosca Cormaic (The Instructions of King Cormac).

"O Cormac, grandson of Conn", said Carbery, "What is the worst pleading and arguing?"

"Not hard to tell", said Cormac.
"Contending against knowledge,
contending without proofs
taking refuge in bad language
a stiff delivery
a muttering speech
hair-splitting
uncertain proofs,
despising books
turning against custom
shifting one's pleading
inciting the mob
blowing one's own trumpet
shouting at the top of one's voice."