In addition to the other commenter, I think you’re exactly right, it was in poor taste, but it is also a storytelling device to show that the Lannisters will do anything to further their climb to power and their desire for legitimacy. I think it also has some world building value as it shows that, 1) a mark of a true great old family house is to have a sword of valaryian steel, 2) the starks are a great house, 3) the Lannisters are not, because they have no valaryian sword, but 4) they are willing to do underhanded things to obtain such an honor. It presages the downfall of Stark and the rise of Lannister, and a changing of the times, because it was a very ignoble act, but no one spoke up or tried to stop them.
In addition to the other commenter, I think you’re exactly right, it was in poor taste, but it is also a storytelling device to show that the Lannisters will do anything to further their climb to power and their desire for legitimacy. I think it also has some world building value as it shows that, 1) a mark of a true great old family house is to have a sword of valaryian steel, 2) the starks are a great house, 3) the Lannisters are not, because they have no valaryian sword, but 4) they are willing to do underhanded things to obtain such an honor. It presages the downfall of Stark and the rise of Lannister, and a changing of the times, because it was a very ignoble act, but no one spoke up or tried to stop them.