Actually Al Nimr was calling for open conflict with Al Sauds and said his loyalty was with Iran. Saudi Arabian government is fucked up for executing him. But it is what it is. Tweets from Kirk H. Sowell below:
I read all of Kirk H. Sowel's tweets and nowhere do I see anything suggesting that he was calling for open conflict with the Sauds. Naturally, any calls for government reform will be hostile to the royal family. What you posted basically shows that he was executed for mocking a royal family member.