There is no "anti-Android bias." Marco is one man, and does not want to make and support an Android app in addition to making a web app, iOS app, and the backend to support the two.
There is also not a good profit motive for him. Android users, on average, not only use fewer apps, but especially buy fewer apps - very few paid apps on Android are as successful as iOS counterparts.
As for Readability, I use the excellent mobile web app. I will check out the iOS app, I suppose, but for Android phones the web app should be fine.
I agree that Marco's decision not to develop an Instapaper app for Android doesn't itself reflect an anti-Android bias. There are plenty of good reasons that could be behind that decision.
However, if you think Marco himself isn't full of anti-Android bias and contempt, you haven't been paying attention. Check out his Twitter feed. Or his blog. Aaron Pressman at The Orange View has captured more than a few examples (as have others, I'm sure).
Marco likes to talk about how he hasn't seen a good Instapaper Android app and how that "proves" there's no market for him on Android (conveniently dismissing the official ReadItLater app, not to mention the pile of apps using the ReadItLater API that preceded it).
Personally, I think there's a much simpler explanation: Any developer working on an Instapaper Android app couldn't help coming across Marco's opinions on Android. At that point, I'd expect most good Android developers would decide that they had better things to do than to writing an app for a platform their API provider hates.
There is also not a good profit motive for him. Android users, on average, not only use fewer apps, but especially buy fewer apps - very few paid apps on Android are as successful as iOS counterparts.
As for Readability, I use the excellent mobile web app. I will check out the iOS app, I suppose, but for Android phones the web app should be fine.