This is the Slippery Slope Fallacy writ plain.
A great many DSLs are stable over years or decades. By your reasoning, a stable DSL is bad because it's going to grow. Why is it going to grow? crickets
Peeling away the fallacy, we could perhaps agree that "the uncontrolled growth of a DSL is an evil best avoided." Or if I'm being less generous, we could look at the bottom of that slippery slope and conclude "general programming languages are bad," because that's what the author seems most incensed by.