@kevteop:
I think you might underestimate the kind of sh*tty clubs you sometimes may find yourself playing

, or also the working knowledge of the musician coming in.
Some of the places we play are equipped with close to nil when it comes to bass amplification. As in, a broken down, static-ridden Behringer DI as the choice du jour. I've found that 95% of the guys I talk to before the show are really receptive to my mic option, and if they're not than so be it.
I always poise it as a question, and offer another option. Like "hey, I don't know what you planned for bass tonight... but I've got a really nice even-response mic and stand, if you want to use it." If they are insistent on using their particular setup, then that is as far as the conversation goes. Usually, the sound guys are open to hearing some info from the band.
And on multiple occasions, I've offered up my mic and stand before the show for ALL bands. If it's a nicer solution than the house equipment (which in most cases it has been), they'll end up using it the whole night. No major setup adjustments, they're happy because sound went well, bands are happy because they're benefitting from it, and I'm happy because I get to hear my mic in action.
Yes, it is the sound guys job to make the band sound the best as they can with what they have, but that also includes input from the band themselves. You shouldn't come into the situation (either party involved) and assume the other guy doesn't know his gear or what he's doing. Either of you wouldn't be getting paid if the other didn't exist.