Not dumb or dangerous, in my opinion, unless you were running in full stealth mode to begin with.
Stealth really only works if ALL your ports are operating in that mode. If you're running in full stealth mode your network is invisible to all pings and port probes and it will appear to a hacker that there is nothing there. If you have a bunch of stealth ports and a single "closed" port, a port probe directed at you will reveal that there's something alive there, potentially blowing the cover off all the stealth ports.
