I do not agree.
1) The person leading the battle is the one written down on the roster, I do not mean any tactical leading, just the name on the roster, so he either personally makes sure everything is as it should be or trusts smbdy (from his clan who can invite people) enough to rely upon him even when still bearing the responsibility for the actions in the battle. Attacker/Defender does not matter, the side which builds intentional skyladders (and leaves them like that for the archers to misuse it) should be held responsible.
2) You may choose not to invite randomers in your team and get in only people you trust - hence you are liable for your team.
3) Even as a randomer, the person should try their very best not to breach the rules as if you get punished for their actions you will most likely make sure not to invite these for any of your future fights.
4) You may always break the ladders not to let the randomers build intentional skyladders, if the archers make a fucking skyladder nest with siege shields on its end and the whole team lets them doing so, it is only good that the leader of the team gets punished as he let them do it/did not stop them from doing so.
5) Id much rather take this responsibility for my team than seeing this shit happening every second battle because the "builders" of these skyladder nests can always hide in the crowd of 50 people who, by ignoring it, allow them to do so which in the end is almost the same as contributing to the exploit, aint it? I think the responsibility of the leader is still much better solution than banning the whole team of 50 people who did not do anything against their team building the (intentional) skyladders.