In re: Diversity vs. Fusion
Raksha Bandhan is very clearly a Hindu religious festival - culture is just one aspect of it.
One should not expect Muslims to celebrate it or taunt Muslims who do not citing the example of some Muslims who do celebrate it.
Many Islamic schools forbid even wishing Hindus on such festivals to say nothing of participation - so to expect them to partake is to interfere in freedom of religion.
The same applies to other Hindu festivals which will take place in rapid succession soon.
Equally Muslims should also refrain from seeking to participate in events like Dandiya/Garba where non Hindus are expressly barred by organizers.
Where non Hindus are allowed, any Muslim who likes may attend as per his or her own understanding of faith.