It would be like posting a jokey picture about father christmas getting stuck up the chinney and replyong with a whole article about why lying to your children avout father christmas in inappropiate.
Or an advert for a water park and a reply about how not everyone in the world has enough access to water.
Or sharing a picture of a lovely meal and replying, "you do know not everyone has enough to eat,"
Or a picture of a new car and a reply all about emissions....
All may be valid articles or points but is really dickish to reply in reponse to someone sharing a funny /news/etc.
Id not stick around with someone who kept doing that...