Do Shias know what grave a sin they are committing in regards to Aisha, Abu Bakr and Umar (RA)?

The way they say such hateful things about these sahabis. The Prophet (SAW) said that no one can compare with his sahabis so who are Shia to call the hypocrites? I was shocked when I heard how some Shia call Aisha (RA) and adulteress. Do they not know that what their doing is so grave a sin that it could make them non-believers? Do they not fear Allah?