The sane human being should like and dislike or else he is apathetic insane being.
If one likes the cleanliness, he should dislike the dirtiness; if he likes the light, he dislikes the darkness; likes the safety, dislikes the hurt; likes the happiness, dislikes the misery; likes the justice, dislikes the wrong-doing; likes God, dislikes Satan; likes God's commandments and dislikes the disobedience of God's revelations.
For this reason, God commanded us in the Quran to quit ourselves from the beliefs and conduct of the idolaters, taking Prophet Abraham and the believers with him as a model and example:
Quran 60: 4-5, which mean:
4. You have a good example [to follow] in Abraham [: the devoted friend of God] and those [believers] with him a, when they said to their people [the disbelievers]: "We are clear of you b and of the [idols] which you worship, apart from God.
We reject you c, and there has arisen, between us and you, enmity and hatred for ever, unless you believe in God alone [and then the enmity will turn into friendship.]
But [follow not] the saying of Abraham to his father d: "Certainly I shall ask forgiveness for you, but I have no power to do anything for you against God e."
[Abraham went on saying:] "Our Lord, on You we rely [in our emigration to the Land of Canaan: Jordan], to You we turn obedient and to You is the final resort [after our death.]"
[Then God – be glorified – said, completing that which Abraham said:]
5. "Our Lord, let us not be persecuted by the disbelievers f, and forgive us [our sins.]
Surely, You are the All-Mighty [in Your kingdom], the All-Wise [in Your creation.]"
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a i.e. those who believed and followed him.
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b And we do not befriend with you.
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c And do not take you into consideration.
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d For Abraham did not ask forgiveness to his father, but only after a promise which he promised him with.
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e If He wants to punish you, and I cannot avert the chastisement form you.
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f i.e. do not set them on us, and so they will persecute us.
http://quran-ayat.com/pret/60.htm#a60_4
quran-ayat.com/pret/60.htm#a60_4
Therefore,
it is not allowed that man may ask forgiveness to his parents if they are idolaters associating others with God, but he can ask forgiveness for the 'exclusively devoted to God alone without associate'.