Though I joined PDF recently...I have been a silent reader for years...since 2006 or 2007. I do remember a time when it used to be better. In my observation the downhill journey started bcuz of the trolls(from any side). The trolls/bhakts/(ultra nationalists with low IQ who r too far gone to consider facts and reality) not only spew their nonsense to degrade discussions but they also can entice some sane members to drop down to their level. I have done this...u have done this and I have seen many other sane members do it out of frustration or to stick it to the trolls or for whatever other reason. Due to this the quality of discussion in a thread degrades faster than what the trolls could've achieved on their own.
A second contributing factor in my opinion is the delay in taking action against the first troll post in any thread, which allows enough time for it to take hold and flourish, derailing the actual discussion. This isn't particularly the fault of mods...they r busy with other things and bcuz they r human they r not always on. I feel like this could be corrected by a mod/bot. There should be "respect" points. An automated system that looks at the negative ratings, positive ratings, the amount of posts, past bans, etc. and awards certain "respect" points. Mods should be able to adjust those if a member has an undeserving number of those "respect" points. Once PDF members are armed with these "respect" points, if they see a troll post in a thread, they can report it. That's where the mod/bot comes in. If enough "respected" members have reported that post it would automatically delete that troll post and hand out a 24 hour ban to the troll. Of course it would also work like the report button works now and mods would be able to look at it and take action. This would keep derailment at its minimum and help in keeping that discussion on topic and healthy.
With this timely action against trolls, the saner members here wouldn't feel discouraged and leave the forum. In my opinion this was the downfall...the sane members left whereas the trolls had the courage to stay. Those who left and cite the reduced quality of the forum as the reason fail to see that they contributed to it by leaving.