The only thing to be warned about here is the blowback effect. This is a form of confirmation bias, whereby the victim uses rejection as a means of confirmation.
I was curious to what he meant by the blowback effect, and so my googling eventually led me to The Backfire Effect[1] which is when "in the face of contradictory evidence, established beliefs do not change but actually get stronger".
I don't really see that applying in the sense of obtaining venture capital, as it is well known that you aren't going to immediately walk in to an office and hand them a check for the valuation you asked for. It's going to take a bunch of both hard and soft rejections, but a person isn't usually going to be in that room pitching to these VCs if they don't already strongly believe that their startup is fundable.
This pertains to the conclusion (and thus the premise) of the blog post:
"Next time you have an idea and it gets rejected, I want you to think of these emails."
The message in my comment is, don't allow yourself to fall pray to the backfire effect when people reject your ideas (whether VC, colleagues, etc.). If people reject your idea, it might mean it's not a very valuable idea, as opposed to being an indication that you're on to something that's so radically new and different, etc.
