Not in grammatically-correct English, he can't. Sorry, but editors don't have to spend a lot of time to make sure their writing isn't utterly riddled with basic errors. They simply don't.
If he were just offering a 'writing' bootcamp thing, in which he'd hassle people to put words on the page, talk about structure and what have you, fine. He claims all over the place to be an editor and able to teach people grammar. That's not ok, when he clearly has no grasp on it himself.
Everyone makes mistakes - typos, errors, glitches in the Matrix, whatever - however, that site was absolutely not written by an editor. I'm not going to comment on his ability to write; I've got no idea really. I looked at that site and the first couple pages of a book of his on Amazon, and it all needs editing of nearly all kinds, direly. No editor produces stuff like that; no editor, if he or she had, would publish it, god knows.
While I definitely agree with the sentiment on the website - I too tried to find his books on Amazon just to see what the guy is capable of via editing - there are two authors by that name. The one claiming to be an editor and running a writing boot camp goes by Randall "Jay" Andrews on Amazon - probably to distinguish himself from the other author, Randall Andrews (no "Jay", obviously). Not sure which book you looked at, but just in case of confusion there about the two different authors with the same name listed on that site.
Anyway, back on topic here - GreySentinel - if he really can write/edit - he needs to understand that people are going to IMMEDIATELY check out his website, see all those glaring issues, and go running the other way. He's losing potential customers/students because he doesn't want to take the time to edit up his website. If he IS an author/editor, I just don't understand how he can possibly NOT take the time to fix up his webpage. He's running an online class. He sells his books online. His online presence needs to be -immaculate- if he's trying to sell his services as an editor/writing instructor.
That's not an insult to him (I don't know the man) but it is the blunt truth of it.
I realize this isn't your fault in any way. As you've said, you tried to tell him of this problem and that's really all you can do, as his friend. It's up to him to make the changes or not. Nor were you the "supporter" who was getting pushy and aggressive. You've been polite and not at all insulting towards anyone here, so far as I can see.
As for his personal teaching methods - I have heard he can be blunt and that approach doesn't work for everyone (which is fine, there are plenty other writing instructors out there who do a great job with a more gentle approach for those who prefer a "light touch"). Hence the "your mileage may vary". Some people are fine with that style of teaching and more power to them. I don't think that's the subject that's making some people here kind of go "eeeeh...".
Now if some of his own author friends/former students get rude and nasty when questions are brought up, that's not good. That's not something he (Andrews) can control, of course, but it still reflects -on- him when people consider if they want to use his services. No one wants to be in a class, virtual or otherwise, with someone breathing down your neck, ready to pounce on you if you disagree with their mentor on something while singing praises for every small thing said instructor does. And that's the thing I've been hearing on "the grapevine" which gives me the most pause about trying that boot camp.
I guess I'm rambling now. But I think it would go a long, long way for his credibility here and on other author networking sites (been checking info on a few different writer networks) if he cleaned up his website and maybe dropped a line to the more aggressive of his friends to chill out just a bit whenever someone is skeptical.