Innnocent Ignorance - Overconfidence

I wonder - How many times a person can do mistakes? I mean how many times? There are few things in life, which never change?

So when some one does something - which is not quite right but on the same point of time he did not know that there is something which he should not be doing - so we call that mistake - but thats innocent ignorance which can be ignored by us assuming that it was seriously innocent ignorance.

But - what's up with some dudes who got overconfidence in everything they do, which is completely not at all acceptable - I know many of this kind of dudes.

He will keep doing stuff - which is not good - and its not right to do something like that, if you are handling production servers - client deployment and real live environment - you do not want to be ashamed or you do not want to do somethings on ad-hoc basis; I mean, if you are trying to fix something - say for instance your antivirus, is not working, then it does not make sense to downlaod a virus and let antivirus catch it. If anti-virus catches that virus that means thats working? is that the right solution? may be I will call it overconfidence that dude got ego that he can actually clean the virus manually and has ability to edit executables in hex-editors and remove the virus code out of them.

But - if some one really does not know that there is something called firewall and while troubleshootinng the networking issues, he some how disables it on his pc then its okay - but if a network administrator opens a HOLE in firewall just to test whether he can reach out or not - then its stupid.

and most of these dudes handle some sensitive systems at companies, client sites and public domain. Which scares me! and I know from my experience - everytime they lack professionally. and they do not realize that it might cost them sometime in the bigger loss.

Professionally and Personally - I do not like these kinds of errors - My only question is - Why they can't think ahead or Consult with collegues? is that ego or innocent ignorance or overconfidence? anything - but if its the first and last one! then that should be punished or not?

frustated me!