I've long been a believer in the mantra that leadership should be distinct from the Average Joe; that the people running politics - big and small and in between - should have class, civility, and respectability. If you think these are just buzzwords, you're part of the group I sincerely hate.
I joke a fair bit that there should be a test before you become an alliance leader judging your ability to stop and think out what you have to say before you say it but it's not a joke. People bemoan how far the forums have fallen since the days where leadership had semi-reasonable and calm arguments on things in full view of the public, but no one is willing to own their own role in this descent.
If you're an alliance leader, your members take their cue from you. They might stray pretty far from the standard you set, but they will subconsciously tether themselves to it. They will evaluate the things, views, and opinions they post based on it. More generally, they'll follow the majority of their alliance, and the majority will follow you. It's why you're the leader.
Having said that, you have an obligation not to be a tool. Leadership is a white-collar job and you should assume that you're meant to show up in a suit, not dressed and dancing like a clown for cheap laughs.
Almighty Grub, as much as I absolutely detest his grand standing for public appeal, does this. In fact a great example of being professional is that we're both willing to admit that we just don't like one another, without going "LOL YOUR MOTHER AND YOU'RE RESPONSIBLE FOR ALL THE WORLDS PROBLEMS." There's a freaking huge line between the two.
But it goes beyond how you present yourself. You can dress a chimp up in a suit, it doesn't make him a banker (albeit he'd be the cutest banker ever). You have to actually know !@#$ to do this job.
If all you know about anything is what a MDP is and how to sign your name, you have no grounds to be an alliance leader. Having good quips doesn't qualify you to run a McDonalds, much less an alliance where real people depend on you to keep the world from smashing their faces in and undoing quite a bit of work.
If you're met with someone irrational, it's far and away appropriate to respond with an endless hail of nukes. I'm not saying we should all be Buddha and run around playing the unshakably reasonable and complacent.
I'm saying you've been tasked with a job by your membership. You have an obligation to ensure you, and by extension your alliance, do not act like tools. You have an obligation to be reasonable and agreeable, even with those who absolutely hate you to your DNA, before deciding to turn it into a blood feud.
Not even trying will turn this game ever more quickly into a gigantic pile of !@#$.