What's extremely unethical is contacting the person over LinkedIn. It's extremely aggressive and a huge violation of boundaries, and proves that Microsoft is sharing personal information (names of users) with Canonical.
If I buy something online from a store, I would expect a few spam emails. But it would be completely unacceptable if a sales representative showed up at my house (despite me only sharing my address for billing/shipping purposes). This is basically what happened to the Azure customer.