Rob doesn't owe this user anything. Nothing. Not even a reply.
He's being nice by responding at all. The passive-aggressive undertone to the user's questions - trying to evaluate the project to use it, and freeload on Rob's work, rather than take it as a starting point for further customization and personal stewardship, while criticizing things like performance before he's measured anything - this is pretty hard to swallow.
Rob may have responded to the cluelessness a little harshly, but it's hard to hold everything back when you're in a conversation with someone like this. And I don't blame him, because like I said, the guy wasn't owed anything.
Users like this aren't the "customers" for a piece of code like this. This is a seed file that you hack and customize for your purposes; it's not a library that you simply link in, or pull from upstream on a regular basis. The right thing to say to a user like this is: go away; this is not for you.
The what?
I stand by my opinion though. If you tell this to any single user, you're just being a mean person for no reason and you are the reason they are unlikely to understand what the issue is about. Maybe that user just read the message and wrote to people he knows "I'm never using opensource projects from github, and this maintainer is the reason." - how does that situation improve in the community?
Rob could end it in so many different ways that would be less aggressive. He didn't even say "learn how github/FOSS works and then check the project again", just "don't come back". It sounds like it's us-vs-them and "they" cannot be expected to learn and improve.