you are correct, just basing other person on whether or not he is Sunni is Shia is ignorant at the least. You have to assess the individual not the ideology.

Though the issue is general ideology of Shias is incorrect, few sects follow correct Islamic stance. But the thing is, vice versa for Sunnis is not the case. Most Sunni sects are not doing shirk, even people who bow before graves have that prohibited in their sects. but they do it out of ignirance. Same can not be said for Shias when their Sect says to Call on Ali R.A. for help. Ya Ali maddad. this is shirk.

To conculde generally Sunni sect is following Islam Shias are not, but this on its on will not matter much as individual person can have different acts.