No one's going to chalk the sidewalk or march around the streets over Psalms. Unlike many other Biblical texts, Psalms has never been at the center of controversy. While the poetry certainly has an agenda, it isn't as explicit or damning as other books.
Psalms wants the reader to worship God, and warns what will happen to those who don't do it, but it also wants to tell people. Think about it; when you're writing a book of laws, it's easy to offend people's sensibilities—take, say, any referendum ever. But Psalms is poetry, and the writers want you to like it.
Most often these days, Psalms is used as a comforting message to the observant.