If someone offers criticism of Barack Obama, I find that the criticism is easier to accept if the speaker has already sufficiently demonstrated their support for Senator Obama's candidacy.
Put another way: If you want to be taken seriously, it helps to prove your bona-fides.
To be clear: I'm not speaking as a DU Administrator here. My purpose is merely to offer some helpful insight to those of you who don't seem to understand why you are not showered with rose petals when you offer your special brand of constructive criticism here on DU. Allow me to explain.
If you have spent the last six-to-twelve months trashing Senator Obama here on DU, and since the primaries ended you have not given any credible indication that you are now a supporter of his campaign, then if you post a thread about how you are incredibly disappointed in him because {insert reason here}, people are likely to wonder about your motivations and conclude that you are still trying to derail his campaign.
I'm not saying they're right. I'm not saying it's fair. What I am saying is that it is virtually inevitable.
So, if you want to be taken seriously -- if you want your constructive criticism to be accepted as constructive -- I humbly suggest that you put some effort into demonstrating that you actually want our guy to win this thing.