an imam at a mosque doesnt have the authority to offer anything outside of his own opinion.Yeah OK that's not what "moderate" sunnis are saying in mosques, in private.
the imam at the muslim center right over here in flushing, queens said that a marriage between a sunni and shia is invalid. You not fooling anybody breh.
It doesn't matter what anyone thinks, what matters is what the Quran and Hadith say. And its clear that its strictly and repeatedly forbidden for a sunni muslim to accuse anyone (not limited to Shias) of being a non muslim
read this
On the prohibition of takfir (a Muslim calling another Muslim a unbeliever): | Islamopedia Online