Shaikh Fawzaan says: They want differing in Aqeedah through this statement
May Allah be good to you, this questioner says: Assalaamu akaykum wa rahmatullaahi wa barakaatuhu, some callers put forward a principle, they say that indeed it (brings about) unity: “We unite upon that which we agree and pardon each other in that which we disagree in.”
If this agreement is (already) in Aqeedah, then yes (we can excuse each other in other issues besides Aqeedah) as differing may occur in the subsidiary issues. The Mujtahid’s (ijtihaad) is taken when he’s correct and (the ijtihad) is abandoned if he opposes what is correct. So if there is agreement on the Aqeedah and the differing is only in Fiqh and subsidiary issues then (this affair is looked at from another) an angle. 
However if this differing is in Aqeedah, then upon what can we agree?! We cannot agree on anything. This is what they want apparently (i.e. excuse one another in Aqeedah issues) and this is not permissible.