This has never happened to me, and I hope it never does but I have something to say about it anyway because it does happen, I've read about it.
Just because somebody isn't knitting (or crocheting) the way you do it does NOT mean that they are doing it wrong!! I've read a number of posts on various boards I belong to from women who are afraid they aren't doing something right because some woman walked up to them while they were sitting, minding their own business and crocheting (or knitting) and told them they were doing it wrong. What gave you the right to tell ANYONE they were doing something wrong just because they weren't doing it precisely the way that you do it? Did the article they were making look like it was supposed to look? If it did, will you please tell me why you told the person that they were doing it wrong? IMNSHO, I think some people probably quit crocheting/knitting after having encounters like this and that's a crying shame. No one should be made to feel embarrassed because s/he knits/crochets the way they do.
Knitting and crocheting is just like any other art-open to interpretation. There are as many ways to hold the hooks, needles and yarn as there are people who crochet/knit. Every crocheter/knitter will tweak a pattern so that it fits her style/shape/taste so just because it doesn't look like the one you made doesn't automatically make it wrong.
What's right is what's right and comfortable for YOU, not what someone ELSE thinks you should be doing.
If you ask me, if we all crocheted/knitted exactly the same way we'd all get bored with one another really, really fast.
So the next time someone stops and tells you that you're doing it wrong just smile and say "Thank you." Then continue with whatever you're doing.
All of the above is my own opinion-YMMV ;)
That was my rant for today, stay tuned.