I disagree. Simply phrasing it as a suggestion to fix problem communication skills is too general to really be helpful. Most people who speak English who are terrible communicators don't realize it so they won't think it applies to them. Meanwhile, foreign founders with strong accents won't understand that it is really them he is speaking to.
I think it is much more helpful to tell somebody plain as day: if you are bad at X you aren't likely to be successful until you fix it. These are facts. Ignore them if you choose but that doesn't change that they are supported by very strong evidence from somebody with loads of experience.
I do agree with the previous comment that he shouldn't have responded, though. It's a losing argument because those who are choosing to misinterpret a statement that is pretty much crystal clear are doing so because of inherent biases. You won't convince those people to consider logic so it doesn't pay to expend time and reputation having a public discussion with them. The people who agree will say so or say nothing and choose to take the advice and act accordingly.