> They know Java, they argue, so why bother with XSLT? 

One good reason: Java doesn't do the job easily.

Since they should be separation presentation from business logic (least of
all database logic) they should already understand that Java is not a
presentation language (not that HTML is much better, but that's another
problem).  There is a mismatch between the job to be done and the tool
(Java).   Having Java tools create XML for presentation manipulation via
XSLt is a good architectural separation of function that allows each tool to
do what it is good at.

I would also agree that you should consider eliminating JSP's altogether.
With a good XML/XSLt framework the days of having to mix presentation
semantics and syntax should be rapidly disappearing.

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list