Not the first important issue they have blocked.
Check it out:

Twitter blocked a petition campaign Wednesday to protect Houston pastors from having to hand over to the city government all of their sermons and personal emails dealing with the issue of homosexuality.

The Christian organization Faith Driven Consumer’s Twitter hashtag campaign #HoustonWeHaveAProblem was censored by Twitter minutes after launching so that users could not Tweet the petition and a warning was placed on Twitter-based links to the petition website. The group’s previous campaign #iStandWithPhil defending Duck Dynasty star Phil Robertson was also blocked by Twitter at one time.

“We are asking Twitter to immediately unblock thousands of people who have already flocked to our petition and want to spread the word from coast to coast,” Faith Driven Consumer founder Chris Stone said in a statement provided to The Daily Caller.