A concert is an agreement between the host/venue and the artist. The booker should research the artist and get the basic vibe. The artist with strong or suggestive material that may not be obvious from their website should say so. If it’s not a fit, you move on.
If you want to be political (this applies to more than music) you will pay a price for it. An activist is someone willing to pay the price. But if you are excellent at political/suggestive music (a la Ani DiFranco, Roy Zimmerman, Eric Schwarz) there are also rewards… including a very loyal audience.