Are all biblical doctrines equally essential?
Affirming every biblical doctrine is essential for perfection. But because perfection is not what God has to have from us, it is not all essential for being a Christian and living a life that is useful. God uses imperfect people, both doctrinally and morally. So, no, I wouldn't want to put all doctrines in the same category of essentialness.
The deity of Christ, the centrality of the cross, the necessity of faith, the necessity of a transformed life by the power of the Holy Spirit, and the sovereignty of God over all things—these things are right at the center. Whereas the nature of spiritual gifts, the timing of certain eschatological matters, and the mode and timing of baptism I am going to put further to the edges.
When the world sees the church squabbling over these things, I think it could help them if we say out loud, "We acknowledge that there are disagreements among Christians. We're sinners, we're finite, we don't have the whole picture in front of us, and we all make mistakes. Just understand that we don't insist that every single "t" be crossed and "i" be dotted. There is variety, and we have to learn to live with that variety. Nevertheless, it's not so mushy that we don't know what we believe."
I think the world can see and handle that. And if they hear an attitude acknowledging that there are Presbyterians, Methodists, Baptists, Episcopalians, etc. among us, and if they see us not throwing hate bombs but love bombs over the wall—expressing "I love you Presbyterian," or "I love you Episcopalian," or "I love you Catholic," or whatever (that is, they see love going out, not necessarily organizational unity)—it seems to me the world can see that, understand that, and sometimes even be impressed by it.
We point people to Jesus when they wonder, How can all these disagreements be understood by me as an unbeliever? I say, "Just go to Jesus, and let Jesus instruct you in the Gospels. And then begin to work towards the fuller understanding."