No harm in apostate touching Muslim parents when burying them
20-2-2015 | IslamWeb
Question:
Should an ex-muslim be banned to touch his parents body at burial
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We are not aware of any Islamic evidence which prevents the apostate (ex-Muslim) from touching the body of his (Muslim) parents at their burial. The impurity of a disbeliever is abstract and not tangible. Therefore, he is ruled to be pure even after his death. Ibn Qudaamah 
said: "The scholars of our School (i.e. the Hanbalis) did not differentiate between a Muslim and a non-Muslim because of their equality in humanity and in life."
Zakariyya Al-Ansaari (from the Shaafi‘i School of jurisprudence) said in Asna al-Mataalib: "As regards the human being, this is due to the words of Allaah (which mean): {And We have certainly honored the children of Adam.} [Quran 17:70] Honor requires that they are not judged as impure by their death; this is both in regard to a Muslim and a non-Muslim. As regards the words of Allaah (which mean): {Indeed the polytheists are unclean} [Quran 9:28], what is meant by it is that their beliefs are impure and that they should be avoided like impurity, not that their bodies are impure." [End quote]
Finally, we should point out that one must advise the apostate and explain to him the evil consequences of apostasy and that it leads to loss in this worldly life as well as in the Hereafter.
In case he is not deterred, then in principle he is like all other non-Muslims; he should be shunned and not kept company as long as he is an apostate from Islam, unless there is a benefit in keeping company and keeping ties with him, like if it is expected by this to call him to Islam and bring him back to Islam from apostasy. In this case, it is permissible to interact with him. For more benefit, please refer to Fatwa 87672.
Allaah Knows best.