Certain large and (inappropriately) politically-ambitious nonprofits overtly supported Proposition 8, abusing their special tax status to do so - my thoughts as a Libertarian on Prop 8's passage are here. What can we do about it? You can, like I did, and like this person did, and like thousands of other people are doing, file an IRS complaint. Guidelines are here. It took me all of 10 minutes.
If you have any hesitation, be reminded of the words of the immortal George Carlin: "Tax 'em! Tax the motherf***ers!"