Pixel peeping is nothing more than the photographic equivalent of a jeweler using a loupe to look at gemstones, or a collector using a magnifying glass to inspect a rare baseball card or coin, or good car detailer getting in really close to check out the condition of the clear coat or paint, and his/her detailing job, or a developer taking a snippet of code out of an application that is over 1M lines to measure that section's execution time, guaranteeing it performs optimally.
There are many professions and hobbies that employ the act of "getting in close" to verify the quality of the product they are creating. Does that make them anal? No, but as a business owner, those are the types of people I want working for me. There is always the risk of being too much of a "perfectionist" however, and that has to managed accordingly.
If I care about the quality and details of my photographic deliverables, I will most likely, at some point, view my images at 80-100% of the resolution to see what is going in the image, whether I am looking for artifacts from the camera, lens, or my post processing skills.
If a person ridicules this practice and demeans those that do it, then they are ridiculing professionals in many industries all over the globe, and in my opinion, that makes them seemingly ignorant, or at a minimum, petty. When they are laying on a hospital bed, and are being run through all kinds of technology (MRI, Xrays, etc), they should remember both the hardware and software were scrutinized down to each line of code and and each component of the hardware to make sure a person isn't injured or killed by use of that equipment. That is the equivalent of pixel peeping in the medical industry, and that very act has a purpose, in many industries.