I've seen a lot of Lutheran baptisms, and I've actually never seen anyone sprinkled. Baptists say Lutherans sprinkle all the time as a derogatory term.
Generally, Lutherans pour (affusion), I would have to admit some are rather stingy with the amount of water.
In any case, scripturally, we can see the modes of baptism in the Bible. Biblically, one can prove sprinkling or pouring but there actually isn't a provable case of immersion in the Bible. People read into the passage that says Jesus went down into the water and came up out of the water as immersion but it isn't speaking of that. If you walked down into ankle deep water, stood there while you were baptised and walked back up onto dry land, you would perfectly fit.
This is revealed by the almost identical language used for Philip and the Ethiopian where is is said of both of them that they went down and came up. Now if that language proves immersion, then the proper mode is for both the person being baptised and the person doing the baptism to be immersed. Even those practicing immersion only don't do that.
Immersion though is within the meaning of the word and the mode is not the important thing. The problem comes that if you are dealing with someone who says they must be immersed, that they are often missing the important truths about baptism and what it is. This is a concern because when one embraces wrong teachings, then where is one's faith?
Marv