Ah, religion rears its ugly head, pretty much as it HAD to in a discussion of ethics. And YES, religion is ugly.
The concept of apostasy is where some religion claims that it is harmful to the religion for someone to leave a religion behind. Technically, the word apostasy is Greek for "revolt or defection." I believe some of the more famous heresies related to the relationship of the church to people who did not agree with the church's teachings. Consider the Albigensian Heresy that led to a crusade (with the eventual extermination of the followers of Catharism, look it up on Wikipedia.org). Heresy (Greek from the word for "choice") is like apostasy. Someone CHOOSES to be outside the church's mainstream, to leave it (defect from it), so the terms are related.
Religion is not a person, it is an idea. Therefore, it cannot truly be harmed by one person's actions unless that person can show a fallacy in the basic idea. (See also "schism" - but that's another discussion.) Religion is often inculcated, perhaps even deeply ingrained into children by their parents, but ultimately religion is a choice to follow some beliefs without considering whether those beliefs are harmful to others. At least in my mind, it is a case of letting some religious leader decide for you what constitutes ethical behavior. This is the source of religious power and the cause of more than one heresy - that someone could actually make a decision WITHOUT consulting the clergy first.
The church is all about calling down people whose behavior is not consistent with clerical world views. Witness for one example the typical religious stance on homosexuality and same-sex marriage as being harmful to others. This is where I would call BULLSNOT (or similar epithets) because it is only harmful if you can't keep your nose out of someone else's private business. Apostasy falls into the same exact category when viewed in that light. WHO GIVES A FLYING TOOT whether Johnny left the church? His private choice regarding his relationship to God is NOBODY'S business but his. And blasphemy is merely a reflection of someone's opinion as well. In EACH case it SHOULD be taken as reflective of that person's individual choices and nobody else's business.
Religion makes it a point that our relationship with God is personal, but then can't get past the question "Am I my brother's keeper?" This is one case where I go ballistic. Not that there is supposed to be a personal relationship, etc. etc. - but that if it appears MY personal relationship doesn't match someone else's viewpoint, they have to proselytize me. This is usually dangerous from a debate standpoint since I can usually test someone's faith very quickly in any debate.