You're another, is often used from a defensive position. For example, when someone disagrees with us we might respond with... "Well I might or might not be wrong but I remember when you presented those ideas on that new project and you were really wrong on all your projections." As opposed to listening to the criticism and using in to improve our own thinking we attack the person presenting it.

An example of switching the topic to the other persons weakness instead of sticking to the problem.

I may be a little hot on this subject but you're just too wishy-washy, you don't even go to the kids school programs, you wouldn't get up off you're fat behind to help if you had to.