Perhaps they are seeing that they need to moderate their editorial line.
But what's bothered me with them, and a few other sources, is not really that they have published things I disagreed with, it's that the coverage has been so one sided. I expect a good paper, whatever its bias, to stick to certain journalistic standards in terms of presenting facts, getting viewpoints, coverage of stories, and also to have some breadth of coverage, so there will be articles that disagree within the paper on questions where there really are multiple viewpoints.
If a paper does that, I will read them even if all the articles disagree with my perspective, because there is some level of trust i their process.
The comments like someone said above have signalled the issue for a while. I didn't notice it first though with GC issues, I noticed it particularly with Laura bates columns and a few others. You would often have some really critical comments under those regarding her statistical claims and process, that were absolutely reasonable questions or criticisms of her articles, and they were pretty much universally moderated out quite quickly. They ended up publishing an article from the editorial staff asking for input on how to deal with the negative comments on these kinds of articles and many regular posters said, you need to let these comments stand or better yet, tighten up how you edit these opinion pieces in terms of factual and especially statistical claims, just find better writers.
The response of the Guardian - stop putting comment sections under the articles that people were responding to so negatively.
That said it all to me.