My quick sense is that you are right in general and wrong on the specifics. You are basically complaining that the vast majority of your students don't have a prerequisite for your class, but you are not providing any coverage of that prereq, merely assuming it in the class ciriculum. By analogy we could say learning French has it's advantages, and then decide to hold a hard line on only teaching in French. Except given your description of current student preparation, replace French with ancient Babalyonian and you'll see why covering the skill yourself might be advised.

@Alanstorm Thanks for the pointer. Oddly the link in your comment hits a 404, but a search found the page at that exact link.

Did Netscape charge for the browser? I was in school 91-96 and never paid for netscape (of course this was on various flavors of unix). As I remember, but can't seem to confirm, they were charging for server software and had some deluxe versions of Netscape. I do know I asked the Netscape recruiter (sent to MIT) in fall '95 how they planned on making money. His answers are precisely why I didn't go work for them: 1. "You'd be surprised how many people pay us for the browser." and 2. "We can sell advertisements based on where people browse". I didn't want to work for a place that 1. I'd be surprised we were making money, or 2. Did something I thought was creepy and would therefore fail. or 3. Sent someone dumb to recruit at MIT. Before I interviewed I actually couldn't imagine Netscape failing, after that interview I had a tough time imagining that they could succeed.