Originally Posted by oceanbreeze
Is this about this incident only or the Sunni-Shia animosity as a whole?
Modern day animosity is generally down to Iran's militants committing war crimes in Syria and Iraq generating anger from Sunnis, while on the other hand salafist militant bombings in Pakistan, Hazara shia massacre in Afghanistan, etc has riled up Shias.
Historically there are also issues, but they are not tied to modern day animosity. Personally,I distrust them mostly for historical reasons than for theological reasonsor because of Syria.