I'm not sure this is a good answer. At least, I think the opening could be rewritten. OP mentioned that their grandmother does "horrible things", which at this stage we don't know much about and which could even be abusive! It seems to me that "Maybe you should visit your grandmother not because you care about her, but because you love your mother. Your mother is the one who is expecting your support. By not visiting your grandmother you're denying the support that your mother needs." ignores the context, assumes OP to be in the wrong and rebukes them for it very harshly. — AJM-Reinstate-Monica 53 secs ago

+1, actively showing an interest in spending time with him by offering an invitation is a good way to reasure him that you aren't just making excuses not to get to know him — Lord Jebus VII 56 secs ago

Well, if he'd posted it as a comment it probably would have gotten deleted, so what else was he supposed to do? — nick012000 4 mins ago