To a person who uses religion to manipulate people or a person into behaving a certain way (i.e. a person with a bad conception of God), I'd probably try to first understand how they understand altruism. Then, I'd ask how they came to accept their particular conception of altruism. Afterward, I'd ask them if a better conception of altruism exists than the one they hold and, if so, would they choose to act according to the better conception. If they express they would not, then I'd ask why not and continue the conversation with the aim of convincing them that selflessly serving people is a better conception of altruism than their original view and this new view actually benefits them too, so they should follow it. I'm assuming this person wants to personally benefit from their altruistic acts based on their previous experiences with manipulating people to achieve a certain result.
To a person who uses religion to manipulate people or a person into behaving a certain way (i.e. a person with a bad conception of God), I'd probably try to first understand how they understand altruism. Then, I'd ask how they came to accept their particular conception of altruism. Afterward, I'd ask them if a better conception of altruism exists than the one they hold and, if so, would they choose to act according to the better conception. If they express they would not, then I'd ask why not and continue the conversation with the aim of convincing them that selflessly serving people is a better conception of altruism than their original view and this new view actually benefits them too, so they should follow it. I'm assuming this person wants to personally benefit from their altruistic acts based on their previous experiences with manipulating people to achieve a certain result.