Allah knows best It's really a hard decision to make, you have no right to physically harm them islamically or by following the rules set by the country you live in. I'm probably the worst Muslim around, but I know that our beloved prophet pbuh would want us to invite these people to the true path of Islam. Maybe spark up a conversation introduce yourself and let them know that the mosque is not a Shia mosque and that "you have never seen Shias" come into a Sunni mosque. See what they say These people are in my honest opinion more lost then a Christian or Jew so we should work that much harder to Inshallah help them Salamis