To remove Xcode, simply run the line shown in the above message:
sudo /Developer/Library/uninstall-devtools --mode=all
# NAME
# uninstall-devtools -- Meta-script for running the various devtools uninstaller scripts.
#
# SYNOPSIS
# sudo /Developer/Library/uninstall-devtools --mode=all
# sudo /Developer/Library/uninstall-devtools --mode=xcodedir
# sudo /Developer/Library/uninstall-devtools --mode=unixdev
# sudo /Developer/Library/uninstall-devtools --mode=systemsupport
#
To remove the Developer folder:
sudo /Developer/Library/uninstall-developer-folder --mode=all