find ~/TESTDIR -mindepth 1 -type d -not ( -name "keepMe" ) -exec rm -rf {} ;

# List what's inside directory we want to remove
$ ls
file1  file2  keepMe/  removeA/  removeB/
＃　Testing what find gives without removing
$ find ~/TESTDIR -mindepth 1 -type d -not ( -name "keepMe" )
/home/xieerqi/TESTDIR/removeA
/home/xieerqi/TESTDIR/removeB
# Actual removal and testls
$ find ~/TESTDIR -mindepth 1 -type d -not ( -name "keepMe" ) -exec rm -rf {} ;
find: '/home/xieerqi/TESTDIR/removeA': No such file or directory
find: '/home/xieerqi/TESTDIR/removeB': No such file or directory

$ ls
file1  file2  keepMe/