I think you are missing the main point that the article is arguing.
You're right about Google. They do not need Skype, but the article does not say anything about Google needing Skype at all. The article only said Microsoft needed Skype. It was a defensive measurement on Microsoft's part.
I think this is the most important sentence of the article: "Were Google to buy Skype they’d convert those 663 million Skype subscriptions to Google Voice and Gmail and in a swoop make parts of Yahoo and MSN irrelevant." This is important for a number of reasons.
1. If Google were to buy Skype, the 663 million users would probably convert to Google's search engine - if they have not already - and not use Bing, which Microsoft has invested heavily in.
2. By buying Skype, Google could force the 663 million users to only register with a Gmail account. Meaning, those with an MSN email account would be forced to convert.
3. Google would also integrate Google Voice with Skype. With the two utilities working together, they would make an incredibly powerful tool, and the users might start to rely on the two combined utilities. This would mean the users would want the utility on their phones which entices them to buy an Android phone and not a Windows phone.
4. With the buy, Google was looking ahead in the future. They could integrate Skype with Google TV. (Which I know was first a failure, but they are still banking on the idea. They'll come out with it again soon enough.) They would also integrate with Chrome OS, and, if the users come to rely on it heavily with the integration of Google Voice and Android, then it would entice them to us Chrome OS and not Windows.
I think Google had much more use for Skype compared to Microsoft. So, Microsoft did not buying it to go after the consumers of Google and Apple; instead, they mainly bought it to keep their users.