Grammar nazis are to this community what excrements are to gold.
"Excrements" is not a word. I believe you're looking for "feces" or "excreta". Or, alternatively, "A grammar Nazi is to this community what a pile of excrement is to gold."
Wiktionary disagrees...it notes "excrements" as plural to "excrement". Also note..."excrement" can refer to any bodily waste product, so even if one considers "excrement" as a mass noun in most contexts, it still could make sense to say "excrements, like sweat, urine, or feces" (similar to fish vs. fishes as a plural).
A grammar Nazi is to this community what a pile of crap is to gold. There, I fixed it.
Riches cover a multitude of woes. -- Menander