If I esteem mankind to be in error, shall I bear them down? No. I will lift them up, and in their own way too, if I cannot persuade them my way is better; and I will not seek to compel any man to believe as I do, only by the force of reasoning, for truth will cut its own way. Do you believe in Jesus Christ and the Gospel of salvation which he revealed? So do I. Christians should cease wrangling and contending with each other, and cultivate the principles of union and friendship in their midst; and they will do it before the millennium can be ushered in and Christ takes possession of His kingdom.

Joseph Smith, in History of the Church, 5:499

Quoted here: (Jeffrey R Holland Ensign Article: 
http://www.lds.org/liahona/2012/08/standing-together-for-the-cause-of-christ?lang=eng

And partly quoted here: (Teachings of the Presidents: Joseph Smith): 

http://www.lds.org/ldsorg/v/index.jsp?hideNav=1&locale=0&sourceId=1b28b00367c45110VgnVCM100000176f620a____&vgnextoid=da135f74db46c010VgnVCM1000004d82620aRCRD