Wiki is not reliable on any controversial subject, and Thaddeus Stevens is still controversial.
Consider this Atlantic article: http://www.theatlantic.com/entertain...incoln/265073/
The guy writing this actually thought that the movie's Thaddeus Stevens was an antihero! It is true that the movie allows people to interpret Lincoln's moderation in a wholly positive light. It is also true that this version of Stevens is there to put his leadership into context, for those who choose to watch the movie.
In particular, the Doris Kearns Goodwin contribution (slight as it truly is) is waved about in reviews as proof that the takeway message really is that compromise, including moral compromises, are true leadership. I think that if you assume that you are misreading your own beliefs into the script.
Yes, you can think for example that Lincoln's observation that scolding slavers will not convert them is clever. Or you can make your own observation that the idea of waiting upon the conversion of slavers is merely superficially practical. That in fact it assumes that nothing can be done without the approval of people who will never consent to the loss of their power, which is not practical. This assumption is manifest folly.
In this movie, Lincoln puts the Thirteenth Amendment ahead of a chance to make peace. It is very likely that the movie took a chance association between the amendment vote and the commissioners' visit to replay in small the choice that Lincoln made at the outset of his term. He refused to give up the restriction of slavery in favor of a peace. In 1861 it was merely refusing to abandon his platform of restricting the expansion of slavery, instead of abolition. Nonetheless, Lincoln chose war over defending slavery any longer.
A lot of people want to interpret this movie as current political commentary. If you do, imagine President Obama being confronted by Tony Kushner, asking the President to try leading for a change.