Walk a mile in another mans shoes. Before you cast the splinter from your brothers eye, look to the plank in your own. Why did you exclude your co-worker? What was their explanation for their behaviour?
If I was the prime supporter of a system and was excluded from rewrite discussions there would be a number of things that would be going through my head. Top of the list would be "Why am I being excluded from something that everyone knows is my area of expertise, is this a move towards me being fired"? At which point emotions will quickly escalate and rational thought will take a back seat because being fired has far wider connotations than ceasing to work for a company.
If I knew that someone was the prime supporter of a system I was assigned to rewrite they would be the first person I'd include. The system has been deemed "not fit for purpose". The insights they could give might bridge the gaps between the perception and the reality. I have seen systems been declared "not fit for purpose" and projects spawned to write a replacement without there being a clear communication of precisely how the original was "not fit for purpose". This condemned the project to deliver the next generation of "not fit for purpose" software.
I agree that sulks and strops are not the way to deal with stuff but one person's sulk is another persons withdrawal to get ones emotions in check and to think things through.
I appreciate all the comments. Just a little more background. The print engine is currently crashing and randomly not printing things properly. A couple co-workers, not the person that supports it, spent three months trying to fix the memory leaks and set the print engine right. After three months things were better, but some things could not be completely fixed including it randomly crashing and on occasion it would be missing a print page in the middle of the print job. During these three months, the co-work that supports the print engine made no move to try and fix things, which is why these other co-workers had to get involved in the first place. The interesting thing is after I wrote this article and tasks were assigned to the co-work that currently support the print engine to get them involved, they didn't do the tasks they were asked to do. It is a bit maddening as they wanted to be involved, but once they were involved they didn't do what they were supposed to do. So again, another co-worker has to do what was assigned to them to meet project deadlines. There is more to say, but I think I have disparaged my co-work enough.
Ben