It is not only about "clan members". It is about every single class follow his /duty.
You are taking a spot in a certain class = you are taking responsibility that this unit (you) will play like this gamemode tells you to play. You have no right to "waste" a spot. If you want to - you pick civ class.
You are saying that this rule (clan member shooting) will ruin your gameplay because it will force you to shoot clanmates. But is it really true? Because there is always a right solution - to play in the same team. But the state of PTP`s clans is... Well, you know, if you will open "clan rules", you will see there is something like "do not shoot clanmates", but you will not see "play at the same team". I wish to say that clan leaders have ability to change it and make it normal, but i was not able to do it in PPLV. So, the question is: how is it possible that one clan at the same time trying to kill AND protect president? Obv that this is nonsense. Clan is a ONE UNIT. Because if it is not, what is the point of this clan (under the idea of existing inside this gamemode, where you have "team competition among classes to kill/protect president")? The same thing for clanless players, when they do not shoot opposite team members.
Like always, there are two ways to solve it:
1. Having normal community with understanding that "gamemode>everything" and playing your roles like this server tells you.
2. Not having normal community, so you need to force everyone on the server to play it in a "right" way. You are making rules etc to do it.
You can not change "state of mind" of this community by just saying "lets try to play like we were playing 8 years ago". Do you expect that if you will do a rule which will force community to play "unnormally", community will like it? Because this downfall from "how we were playing" to "how we are playing now" was not instant. Do you remember how 1-2 year ago there was a topic where someone said something like "i am doing a list of ptpers who will shoot everyone who is on opposite team, sign if you want to"? Was not that bad idea, but it was only a half-measure. Partly official, partly optional.
When newbie is starting to play this gamemode, he is looking how other regulars are playing it and doing the same. Clan members are looking at their leaders and play how they/their rules say. So, server "leaders"(clan leaders, admins, mods, "popular" regulars) is the key, and in our case it is very mindless key.