Is he wrong? I know nothing about lactose intolerance so I looked some stuff up online. This site says that the lactose intolerant usually can consume 7 g of lactose without a reaction, and also that butter has only trace amounts and can usually be consumed. This site and this site seem to agree.

I'm not saying s/he's right, and s/he was spectacularly wanky about explaining their point. I'm just saying that a couple minutes skimming Google results for webpages that looked moderately informative seem, on the surface, to support nadsatshoot.