^ No one forced them to show their Indian credentials. They did it themselves, as did the Muslim organizations who decided to not to bury the terrorists in Mumbai
They're doing it "on their own" because of the pressure put upon them by Indian society. I sincerely doubt that they enjoy constantly having to prove their patriotism...but as we're getting news of Muslims being banned from purchasing homes in an entire city as backlash from these attacks, its becoming clear such constant demonstrations of "Indian credentials" are necessary to survive in such a deeply bigoted society.
many temples in pakistan were also demolished but I didn't see pak hindus taking revenge by planning bomb blasts in pakistan.
Perhaps overall they don't feel as vulnerable in Pakistani society as Muslims do in India? They also didn't feel the need to wear black ribbons and carry out special protests to express their disgust at Hindu terror in Gujarat, or on the Samjhauta Express, or Indian war crimes in Kashmir...and nor should they feel obligated to.
In any case, we're not talking about the 1993 blasts, we're talking about last month's attacks, which the Indian government seems to believe were carried out by Pakistanis. And yet, Indian Muslims still are feeling the need to actively demonstrate that they weren't associated with the attacks.