One of my first pet peeves I call anti Catholicism. If you are focused on being anti Catholic, you are not being Lutheran. Being Lutheran is not just about being different than the Catholics. In fact, there are many things we do that are very similar to what the Catholics do. Rather, we simply need to to be focused on being Lutherans. The Catholics will take care of themselves.
Another peeve of mine is the "plague on all their houses" broad side. Christendom has many branches. I do believe that confessional Lutheranism is the one that has everything right - that is perfectly reflects the Scriptures. But simply blasting away at all others is in no way helpful. We must carefully distinguish what it is that each group teaches, affirm what is right and therefore with which we would agree, and that which they teach wrongly. Further, this indiscriminate blasting leaves the impression that only confessional Lutherans are Christians and will be in heaven. This of course if completely contrary to both the Scriptures and the Lutheran Confessions. In short, I have no time for brain dead Christianity.
We have enough problems in our lives in the church and don't need to shoot ourselves in the foot. Both of these do, in effect shoot us in the foot.