The depth of this hurt is attested to by the fact that when a religious sentiment is violated, it can produce a martyr. People connected to a converted person are deeply hurt. Even the converted person will suffer some hurt underneath. He must necessarily wonder if he has done the right thing, and further, he has to face an inner alienation from his community, a community to which he has belonged for generations, and thus, an alienation from his ancestors. I don't think that can ever be fully healed.
Religious conversion destroys centuries-old communities and incites communal violence.
It is violence, and it breeds violence. Thus, for any humane person, every religious sentiment has to be respected, whether it is a Muslim sentiment or a Christian sentiment or a Hindu sentiment. Further, in many religious traditions, including the Hindu tradition, religion is woven into the fabric of the culture. So, destruction of a religion amounts to the destruction of a religious culture. The Mayan, Roman, and many other rich cultures are all lost forever, and humanity is impoverished for it.