I'm probably going to be yelled at for giving a religious lesson here but...
From an Islamic point of view, you are right. Not everyone who calls themselves Muslim is Muslim. I think in today's society people consider themselves to belong in a religion if their ancestors belonged to it, not necessarily because they practice it.
Of course, you can't do things forbidden by God and then claim that you have submitted to God- which is the meaning of Muslim. And Muslim, unlike common belief, isn't just followers of the Prophet Muhammad, it's anyone who submits to the one and only God and who believes in all his prophets and follows God's decrees. So if a Christian or a Jew believes in these things, he or she is also a Muslim. The Qur'an also warns against hypocrites who give the appearance of being a Muslim in open society while not truly believing or following the faith in their private life.
By my definition, most Bollywood actors who have Muslim ancestors (Salman, Saif) appear to be non-Muslim. Shahrukh's parents were both Muslim, but by allowing his wife to remain non-Muslim and he himself engaging in non-Islamic practices appears to be in the wrong path.
Ultimately, and most importantly, we can't know who is a Muslim or not. Only God can know that because only He knows what's in someone's heart. So it is our responsibility to not judge or treat people badly because of our assumptions of them. Everyone's sin or virtue is onto themselves. Only they are responsible for it and only God has the right to judge. Furthermore, you cannot know who is superior in the eyes of God or whose sins God will forgive. So we cannot condemn people. All we can do is follow what we think is right.
Okay now you can yell at me...
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