Vali Nasr writes that

Anti-Shiism is embedded in the ideology of Sunni militancy that has risen to prominence across the region in the last decade. Wahhabi Sunnis, who dominate Saudi Arabia's religious affairs and export their philosophy to its neighbors, have led the charge, declaring Shiites "infidels" and hence justifying their murder. (The legacy of Wahhabi violence against Shiites dates back to at least 1801, when Wahhabi armies from the Arabian Peninsula invaded southern Iraq and desecrated the holy shrine at Karbala.)

...

To contend with Sunni militancy in Iraq, America must contain it throughout the Middle East and South Asia. Among other things, this means putting pressure on countries like Saudi Arabia and Pakistan to stem the tide of anti-Shiite rhetoric in their mosques and media. It also means insuring that Iraqi Sunnis do not feel left out of the emerging democratic Iraq, and working with Ayatollah Sistani to quell Shiite rage over the attacks. What happened in Karbala must not become a sign of things to come for the whole region.

He seems to agree with Michael Scott Doran.