The situation in Bahrain may not be as clear cut. There have been multiple reports that the Saudis are assisting the Bahraini regime in putting down the protests - that they sent in 150 tanks and APCs, which might explain why they’re much more willing to use deadly force than what we saw with the Egyptian army and protesters who expressed a kinship with each other.

Add to that the fact that there’s a sectarian divide in Bahrain - that the regime is Sunni, but it’s the Shi’a majority that’s protesting, and you have another layer of discontent.

The Saudis want to quell the protests lest they spread to their country, which explains the Saudi motivations for getting involved.