We should fear and love God so that we do not take our neighbor's money or possessions, or get them in any dishonest way, but help him to improve and protect his possessions and income.
That I guess would be the official Lutheran Statement on stealing.
Regarding the churches, you might have to be more specific and you might need to at times look into history as to what happened.
For example, the Peace of Augsburg declared that the Prince's determine what the church will be. Thus if you were to accuse Lutherans of "stealing" that church, really it was the Prince who determined what the churches in his Provence would be, the Prince chose not the "Lutherans". Furthermore, though it would be unfair to consider that Prince's stealing it, since it was part of the terms of the treaty. This is just one example that it is not as simple as "lutherans" stole it.
I would also note that it is an unfair statement to paint all of Lutherans-even Lutherans today under anything that happened in the Reformation. No one in Lutheranism today "stole" anything 500 years ago, since they were not alive. They were all born with said churches as Lutheran churches. And it is quite wrong to say then that they stole it. Should I do a family tree, going back 200 years, find out that some aristocrat kicked my ancestors off of their land and go demand it back, and if they refuse call them thieves?