As shown by the hexbear comrade here, a lot of people just assume that no leader equals chaos. I find very hard to deconstruct this assumption, i think because it is deeply rooted in our societies. What i usually do is to point out that it's not leaders that bring order, but organization. Most people then say "well yes, but you can't have good organization without leaders", which is more manageable to discuss, though most of the times people didnt change their mind in my experience. My main argument, which can take many forms, is that there are lot of times in our lives where we organize without leaders : in some families / homes, during trips with friends, when playing casual games or sports, even in some demos or movements.
It doesn't really answer you question, but there's a passage of Bakunin's God And The State that i really like, where they point out that authority does not necessarily mean leader. So if you can convince someone that it's authority they like and not leaders, you can then bring up the anarchist version of authority : restricted in time, matters and always up to debate.
Does it follow that I reject all authority? Far from me such a thought. In the matter of boots, I refer to the authority of the bootmaker; concerning houses, canals, or railroads, I consult that of the architect or engineer. For such or such special knowledge I apply to such or such a savant. But I allow neither the bootmaker nor the architect nor the savant to impose his authority upon me. I listen to them freely and with all the respect merited by their intelligence, their character, their knowledge, reserving always my incontestable right of criticism censure. I do not content myself with consulting authority in any special branch; I consult several; I compare their opinions, and choose that which seems to me the soundest. But I recognize no infallible authority, even in special questions; consequently, whatever respect I may have for the honesty and the sincerity of such or such an individual, I have no absolute faith in any person. Such a faith would be fatal to my reason, to my liberty, and even to the success of my undertakings; it would immediately transform me into a stupid slave, an instrument of the will and interests of others.