Telling people you have all respect possible for their position and then knocking down their comment in this way, I argue, is a fallacy. Both the parent comment to yours and the grandparent comment to yours make a philosophical argument about their own experience and how it made them feel and what they believe are important to their life.

The grandparent comment literally says: "Also, the real meaning of life is to find your creator, not make millions of dollars. When they bury your sad fat rear end in the ground, all you've made goes to someone else. The afterlife is a part of life. Read Acts 2:38." Allow me to break this down philosophically from a few points of view.

"Also, the real meaning of life is to find your creator, not make millions of dollars." -- Whether you believe your creator is a "invisible sky-grandpa", a set of entirely random events that, given enough time post singularity in a statistical manner, created the perfect set of circumstances to create a small blue ball next to a rather meaningless little helium creating furnace, or an all knowing pasta based creator who's noodle-y appendages may touch you in soul changing ways, philosophically speaking is this sentence not true? I would argue regardless of whether you have an all knowing creator or a random set of events, this sentence stands true.

"When they bury your sad fat rear end in the ground, all you've made goes to someone else." -- There is no argument here. When you die, regardless of your beliefs, all you have made seemingly does to someone else.

"The afterlife is a part of life." -- This certainly means different things to a person depending on whether they believe in an all knowing creator or a random set of occurrences. Psychologically and philosophically, a part of the human condition is that coming to terms with the inevitability of your own mortality is always and certainly a part of life.

"Read Acts 2:38." -- This one cannot be argued as anything other than religious. It's definitely a philosophical passage on what a person should do in their life and what the reward of doing a simple act will be. You can discount it if you wish. I see no harm in it.

Your parent comment basically had one sentence of meaning. It was: "The real meaning of life is to find your purpose, so that you don't die meaninglessly". I understand you think this is a "terrible thing to be telling people". But again, philosophically what is the harm in this sentence that makes it so terrible? It seems to me that you and the parent comment are arguing the same exact point. He says "the real meaning of life is to find your purpose" and then goes on to explain that in finding your purpose you don't die meaningless. You argue that "a person's purpose is the sum of their experience." If the sum of their experience is less than another persons does this balanced equation make their life's purpose less meaningful? If so then you have argued the same as the parent comment. If the sum of a persons experience is irrelevant in comparison to everyone else's then I would suggest that it would seem the sum of their experiences is not a person's purpose after all. Deep philosophical points indeed.

Nevertheless, I don't believe you have shown why these comments are terrible things to tell people. These are philosophical arguments about the human condition. Their argument are valid and not terrible to share with others. Yours are also valid and not terrible to share with others. Just as the many thousands of other philosophical arguments within these lines of thought are valid and not terrible to share with others.