PG's stance (my interpretation) is - (1) Founders need to sell to be effective and (2) Having a strong accent makes it hard to communicate effectively and in turn, sell.
I get that (I have an accent myself).
People are objecting to the underlying assumption that this causation is something we deem acceptable. Here's a counter example. (1) Founders need to sell (2) Part of selling is to make the audience identify with you, so founders who look/act like their audience do better. This suddenly becomes a slippery slope, even if that's a perfectly logical argument.
tldr: (Correlation or causation) != acceptable.