Shell survives killing xterm

[Hans Werner Strube]

When an xterm (running bash) is killed, e.g. by twm menu or by exiting the
xinitrc, the bash survives in the background with PPID 1 and has to be killed
manually with kill -HUP. The only way to exit xterm neatly seems to be
calling "exit" in its shell. This is very annoying. Is there a workaround?
As the man page of bash says SIGTERM and SIGQUIT are ignored by an
interactive bash, I tried setting
trap "exit 0" TERM QUIT
in .bashrc, but without success.