There are many systems of moral philosophy. Things that are moral in one system might be immoral or neutral in another. It does not make sense to ask if an attitude or action is ethical or unethical, unless you specify the moral system.
If we could all agree on the best moral system, there would be no such thing as moral philosophy.
Some more precise questions you could ask:
Suppose issue X is immoral in a given system A. Does it follow that indifference to discussion of the morality of X is an immoral attitude within system A?
Do any well-known moral systems A give positive or negative answers to the above?
I will also point out that moral systems tend to concern actions and not attitudes, thoughts, or feelings. An attitude is only moral or immoral if it tends to lead the holder to a given moral or immoral action.
For the moment I will replace X being abortion with X being the action of hitting a newborn baby with a hammer. Most genuine moral systems recognize this as an evil action.
You and your friend see a man in a dark cloak. He has goat horns and a halo of smoky flame. In one hand he holds a newborn baby. In the other he holds a claw hammer. He places the baby on the black granite altar at his feet and raises the hammer to strike.
You turn to your friend. "This is awful!".
Your friend shakes their head "I am not interested in discussing the morality of the situation."
Which of you is in the right? Which is in the wrong. In this example it depends on what you both do next. There are many actions open that are consistent with your attitudes to discussing the subject.
Perhaps you rescue the baby while your friend stands idly by. In this case you are in the right.
Perhaps you continue berating your friend and the baby is smooshed. In this case you are both in the wrong since you did not try to save the baby.
Perhaps your friend rescues the baby, not for any abstract moral reason, but because the crying baby evokes an emotional reaction.
Perhaps your friend recognises the cloaked man as the arch-devil Mamon, picks up a rock, and brains the devil out of hatred. Perhaps he catches the baby after. Perhaps he ignores the baby and it dies anyway. Perhaps he attacks Mamon out of hatred, but as a side effect he gives you the opportunity to catch the baby.
Perhaps your friend is motivated by selfishness. He recognises the baby is his nephew. He hates his nephew and he hates his sister. But if the nephew dies she will become doubly insufferable at Christmas. So he tries to save the child to save himself the frustration.
On top of this, we must consider the potential harm to one or both of you caused by trying to save the baby. If you both know the archdevil Mammon can incinerate any mortal with a mere thought, then there is no use trying to save the baby. You will only get yourself and your friend killed as well.
Even if the man is just a man with a hammer, there is potential risk to you and your friend by trying to interfere.