To answer in this matter is in fact to lie. Stating it has no baring on your life, simply is a way of restating that your individual meaning trumps that of the meaning of life. Those who say this are fall into one of two categories: The Liar, or The Ignorant.
The Liar simply wishes to deceive you. They know in fact the emptiness and the shallowness of their claim, they may not want to confront it, they may simply wish to hide their selfishness but it is there and they know it.
The latter category, the ignorant, they are sadly the least likely to acknowledge any of the importance regardless of argument. Simply put, the ignorant are too benighted to care, nor are they at all deep thinkers. They may be intelligent, smart individuals, but they are so blinded by their own desires and their own decisions, and to some degree what they have learned, that they refuse to acknowledge any wisdom in the pursuit of this question. So Apathy has two camps. Those who know in fact they are not apathetic, but they give the appearance for whatever reason, and those who are but for only one reason blind ignorance.
Again ultimately life has meaning or it does not, this of course means there either is a god or there is not. There really are only two possibilities. While the existence of a god cannot be proven, this existence can logically be inferred. While we may not know the purpose and the meaning of life, we can in fact both infer there must be one by the mere fact we exist. We can also logically see the need for a purpose regardless of it’s existence.
Without intrinsic purpose, and meaning (and therefore a god) then in fact life is truly meaningless. This in fact means that anything does go, while we may be able to come to some simple rules to govern society, those rules are fleeting and subject to the times and in fact not eternal. Look to ancient Germany where the logic was murder was ok because the strongest should do what they want. Look to today where some people will justify a dog (having already mauled a 4 year old) deserves to live and it’s life is equal to the child.
Apathy is in fact the biggest hoax perpetrated on otherwise well meaning people. It makes people feel good to know they are not part of what they consider to be foolish. Yet it is perhaps the single most foolish thought ever planted in the minds of man. It preys on pride, and it festers. Continual apathy in fact weakens the capability to reason over time. The very act of not tackling subjects, especially heavy subjects is not good for the mind. Like the body, your mind and reasoning capabilities need exercise. Choosing not to think about it, choosing not to wrestle with deep questions in fact hurts you.