بسم الله الرحمن الرحيم
All praise is due to Allah, the Cherisher and Sustainer of the worlds, Most Gracious, Most Merciful. May salawat i salam be upon His slave and messenger Muhammad, his family and companions.
Surely being merciful means that God is merciful to people who do not deserve mercy.
Allah SWT gives people to live on His Earth, while they continue to spread lies about Him SWT. Also:
Whoever brings a good deed, he shall have ten like it, and whoever brings an evil deed, he shall be recompensed only with the like of it, and they shall not be dealt with unjustly. That's only something from Allah's mercy. His SWT mercy is greater than a mother's mercy towards her baby.
The problem with the Christian belief is that Allah's SWT justice doesn't fit in it.
Why would God need to be merciful to good people who have done no wrong?
Be aware that shirk, the opposite of oneness of Allah, is the greatest sin and the most dangerous thing can do.
I would not like to see you condemned to hell because you do not follow the Christian beliefs, in the same kind of way you do not want to see your non Islamic friends condemned. The chances are I will go to my grave a Christian, and you will go to your grave a Muslim.
Noone of us would like to see his friends in Jahannam, however, we must know that one who has erred, and who was warned, and who got proofs, and who got time to repent, yet failed to do so really deserves punishment. That's justice. Those who do good can't be the same as those who do evil.
Your faith comes from the same God who gave me my faith, why should I try and change what God has given you? Why should you try and change what I believe God has given me?
Actually it doesn't. Christianity doesn't come from God, subhanahu wa ta'ala. God has given you
fitrah, a natural inclination towards tawheed, my dear friend. It's not rational to say that Allah SWT gives you a faith and is pleased with it, because it's non sense to say that people who believe contradictory things end up in the same manner.
If we are able to forgive and pray for those who are different to ourselves we might see how it is possible for God to forgive.
Iman and kufr, belief and disbelief are things for which Allah, 'azza wa jalla, rewards or punishes a person. We can call someone to Allah's religion, we can advice him, we can learn our deen so as to give our best, but we can't do what's Allah's job.
It has been said that we reflect the God we worship, and the challenging question is what kind of God do I worship?
I don't think that's not true. Nothing is like God, may He be exalted. He SWT doesn't depend on us, and doesn't take anything from His slaves.
And all praise is due to Allah alone, and may salawat i salam be upon Allah's Nabiyy.