Well looking here it would appear that others are having trouble silently removing JAVA as well.

http://forum.java.sun.com/thread.jspa?threadID=692662&messageID=4025805

Try searching Google or the Sun site to see if you can find any assistance on what command line to use.

It has noting to do with KiXtart or the RemoteExec UDF, they can only run the items for you, but you need to find the correct code to do the silent non-interactive removal process.