Is it by our cap
or by our turban.
Is it by our dress code or by their race?
The answer is no.
Anyone can wear a turban, anyone can wear a cap, anyone can dress like a muslim. Islam doesn’t select race.
Now how do we identify a muslim?
A person who is kind, faithful,doesn’t use foul words,doesn’t gossip,doesn’t harm others,forbids evil,doesn’t take bribe,who prays the five daily prayers,who doesn’t engage in immoral acts, who doesn’t oppress, who is generous….and among others.
In a simple way: a person who does good things and forbid bad things.
If you meet a person who dress like a muslim and doesn’t act like a muslim then do not use that person’s actions to qualify the entire muslims. It may be that the person is an unbeliever who just dresses like a muslim or it may be that the person is a muslim who doesn’t practise islam and this makes the person an unbeliever until he repents and follows the right path.