You're right! Doucheing is not recommended. The vagina is self-cleaning, and it's really unnecessary. As mentioned, there are other issues if you're using a chemical or soap (yeast infection waiting to happen!). Yeah, I would stay away from doucheing.
However, this bulb is also meant to be used as an anal "douche" or enema, which is far less dangerous. I hear it doesn't work very well though, and isn't an effective product. And apparently the nozzle is silicone over plastic, so you probably can't boil it, either.