Was I correct to use the word "establish" in my tweet? Should I have included adverbial "as"?

I amused. Person who can not cope with "Cannot modify header information" error should not establish himself a web-developer.

"I am amused. A person who can not cope with a 'cannot modify header information' error should not claim to be a web developer."

That would be a rough fix. An elegant solution would be:

"It's amusing that a person who can't handle a 'cannot modify header information' error claims to be a web developer."

But, in a larger sense, this kind of IT-level sniping is unhappy. If a colleague is having trouble, do not snipe - lend a helping hand.

try:

I'm amused. A person who can't cope with a "Cannot modify header information" error has no business calling himself a web-developer.

or

I'm amused. A person who can't cope with a "Cannot modify header information" error shouldn't pass himself of as a web-developer.

I don't think 'establish' is apt in that context. An alternative could be "consider" as in ...should not consider himself...