Being AFK while in a leveling party in FFXI was always looked down upon. If you had to AFK for a reasonably long time (15 min or more) you were usually asked to leave or find a replacement for yourself and the reason is because the exp system was balanced and everyone had to pull their own weight in a fully functional party. People are making it less of a deal in FFXIV because:
1. Everything is too easy so therefore people simply don't care what happens along as they still get their SP.
2. Since a person being AFK in a party doesn't hold the party back people just don't care.
It's not about whether you care or not, AFK leeching is abusing a flawed system similar to botting obviously both are going to happen. AFK leeching has a lesser impact in a party system than it did in FFXI, is that a justified reason to leech?
Leaving a party doesn't stop them from AFK leeching since they can just form a party by themselves. If you don't care about people abusing the system just don't post, flaming is only going to tarnish your own name and make you look bad.