1) What?
2) I know that, and I agree - its still unethical no matter what happened/who did what
3) Its still not foolproof, even if they pay upfront they can then become the victim (not get the work they were promised) so its still not a win-win situation
4) You had a go at my "worst response you've ever seen." I do not see taking his site down as unethical, Craddock however does own the theme as it was never paid for, so he has every right to take it back (which if he emailed is impossible)

You can't really learn from your mistakes as you didn't really make any. Sometimes this stuff happens. The best you can do is ensure you do the best job, on-time, and fix any problems ASAP. If you know you did a good job then thats there is nothing else you can do.

I wouldn't quit freelancing from just this. Most people you deal with are fine, they'll pay you and not make a big deal if there are any errors (we're only human after all) Its like any industry, even working for someone else you have clients or customers that don't work out well.