The first, because 'we have met' refers to the present meeting. For example 'We have met today to discuss the rail strike.'
But a lot of speakers just see one perfect and have a kneejerk reaction that make them carry on with the perfect willy-nilly. So I expect some users would (wrongly, in my view) regard your second sentence as acceptable. ;-)
A reflex - an action that takes place, regardless of whether you want it to, when something triggers it.What is a kneejerk?