From the original wiki , violent agreement is when two sides are arguing over a particular issue, thinking that they are in 'violent disagreement' *, when actually they agree with each other on pretty much everything of importance.
- Note: Here 'violent disagreement' is not meant literally, only figuratively, hyperbolically.
Original wiki content
Violent Agreement 
Two people are arguing about something. It is clear to everyone else at the meeting that the two hold the same point.
Either the facilitator gets out his RolledUpNewspaper or the arguers will eventually figure it out. That person should then say "I think we are in violent agreement."
Contrast with PolarizingQuestion. See also synonym HeatedAgreement, whose page is undergoing DeprecationRefactor.
Contributors: Eirik Fuller, BillTrost
We used to have a BullshitFlag at some of our BrainStorm meetings. It had other (obvious?) uses, but this was one. -- JimDensmore
Often times, two parties in ViolentAgreement will disagree on why (the conclusions are agreed upon, the premise is not). Or, they just both like to hear themselves talk (and want others to hear it also). ViolentAgreement often occurs with an "audience" present.
That's something else. (At least, that's not the sense in which people use ViolentAgreement on this Wiki.) ViolentAgreement is like person one arguing "Foo! Foo!", with person two arguing "But bar! You need bar!" and it turns out A and B are two aspects of the same solution, called FooBar. (Yet another etymology of FooBar)
[Often times, two parties in ViolentAgreement will disagree on why (the conclusions are agreed upon, the premise is not).]
I HaveThisPattern in arguments with my wife. Our goals are quite well aligned, but our mental models are not, so to speak. We get into ViolentAgreement exactly because we do not understand the others 'why' and assume that the other draws different conclusions. This might be the case, but usually we don't, and it is often quite a strange feeling when we finally get through to that. We often have to get into kind of MetaDiscussion before we realize it, which is hard when the argument gets really heated.