Just to be clear here, there is a difference between gluten intolerance and gluten sensitivity. In a broad sense, no, eating Paleo does not make you either of these things. Celiac disease is defined as a gluten intolerance. In this case, the body makes antibodies to its own small intestine tissue as a result of exposure to gluten and this is why it is defined as an autoimmune disease. It is genetic in nature, but many factors can affect the expression of the gene. I've seen a case of Celiac disease that developed in a 46 year old woman after a course of antibiotics for a sinus infection. Until that time she denied having any symptoms related to anything she ate, so should we say that antibiotics cause gluten intolerance too? Since it is genetically based, eating Paleo can not "give" you gluten intolerance, rather by removing gut irritants it can give the gut a chance to heal. Since there is much inflammation happening in the gut mucosa in this condition, the immune system has a limited ability to react to gluten in this inflamed state. Calm down the inflammation and the immune system reacts to gluten more 'normally' if the predisposition to gluten intolerance or sensitivity is there.
In the case of gluten sensitivity, the inflammation of the gut is present as a result of gluten exposure, but there is not the autoimmune component. However, Dr. Fasano's work at the Univ of Maryland's Celiac center has shown that gluten sensitivity, by inflaming the gut and creating 'leaky gut,' can set the stage so to speak, for the development of other autoimmune diseases in genetically predisposed individuals. This is why some might develop RA, others MS, and others multiple AI diseases and subsequently why we see dramatic improvements in these folks when they adopt a Paleo diet. (Also see Robb Wolf's latest blog post for the link to works by a doc who was talking about this connection over 50 years ago.)
As for your coworker's response, I find this somewhat common in those diagnosed with Celiac disease. Two things I believe are at play here. First, these folks have really bad reactions when they eat something contaminated with gluten. If gluten-free diets are perceived as merely a fad diet, they risk not being taken seriously by waitstaff, chefs, and other food service personnel. Its not like an anaphylaxtic reaction that can be seen immediately, so its' really important that the food service industry understand the seriousness of the consequences. If you're Paleo and going to a restaurant, and if you ask for no bun with your burger because you're "gluten- free" and then chose to cheat and order a beer, this can undermine the seriousness of gluten-free for those that really suffer from it. Also, if you have diagnosed Celiac disease, gluten-free foods are considered "medical foods" and can therefore be deducted as medical expenses for tax purposes. Potentially the "fad" of gluten-free could jeopardize this.
The second reason is as someone else already stated- for a person with a gluten intolerance, there can be a real frustration that they have no choice but to eat gluten free. They wish things could back to "normal" and they could eat all their old foods again. They are tired and frustrated with having to be so careful about everything they eat all the time. From this perspective, it can be hard for them to understand why anyone would voluntarily choose to take on that level care when eating. I think education is really important here and that practitioners can help these patients see that in the end, this is an advantage as they will be healthier, rather then a burden. If we can all agree that the end goal is being healthier, these kinds of situations may no longer arise in the future.