I think I understand what Joe was getting at and I don't completely disagree with him. What I believe is that allowing a disconnect between "colleagues" and "IT" by dehumanizing them to "customer" is a hazardous move. Instead of addressing how we provide service we've instead constructed barriers and disconnected ourselves from the people we're supposed to be helping. Touchy-feely, kumbya, blah, blah. I know.
IT has spent too much time separate from the business. Business leaders still struggle with how to deal with IT and technology because they still don't understand that IT is part of their business infrastructure not some money pit a bunch of nerds constructed. Problem is that IT has liked the autonomy and power that go with maintaining the technology black box. The nerds enforced a power stalemate with the popular jocks that were in the executive suite.
The other problem, as I see it, is that IT has a uniquely global view of the enterprise. Often times the only other group of employees that have that view is executives (and facilities maintenance...don't underestimate how much they know about your business!). This perspective and the fact that business leaders don't understand IT has spawned a feeling of IT Exceptionalism that at times feels like its infected IT industry-wide.
Considering our co-workers, or even users in general, as "Customers" really minimizes the roll that they play in IT's success and widens the chasm that already exists between IT and the business interests it serves. There's obviously an appropriate time to consider users "Customers - when the core function of the business is providing IT services. Obviously, as an IT admin you're dealing with customers in the truest sense in that scenario.
When we need an analogy for IT-types to understand good service we seem to always go with the "customer" one for some reason. As customers, do we experience good service because we're customers? Often we do not. Customer service is not the purpose of the business unless for some reason the business has decided it is how it will differentiate itself (I'm totally ripping off +Rob England here). Profitability is the real purpose. So we're asking IT to treat users as business does - Like sheep to be fleeced and dealt with begrudgingly.
Business can ignore, mistreat, under-deliver, and otherwise abuse customers as long as customers continue to pay. IT has acted that way with users and colleagues all too often in the past and it worked because there was no other way to do things without IT. Now in the days of BYOD, shadow IT, and cloud services IT can be bypassed and users and colleagues are doing the end-run in droves.
Perhaps instead of considering users as "Customers" we should treat them as co-workers, friends, fellow humans, lovers, family. Whatever it takes to have empathy and patience with them. To treat the people we are helping with respect and kindness. We need to understand service and learn what it means to serve. We have a great chance to have a positive impact on our fellow humans in IT. It's always "Service as an Opportunity" - SaaO.