Hey Set!
Great question.
There are reasons to use FLOSS and not agree with the ethical underpinnings.
1. Some of it is unique and provides capabilities not easily achieved on other OS
2. I like the system itself, I am used to using it on a daily basis and changing invokes a cost
3. I like the feeling that I am using something unique (from the POV of most people)
4. I am largely lucky that most proprietary tools I need work well through WINE so I can use the best of both worlds
But also there is a problem that I see in your question: if someone disagrees with Stallman's ethics, then it means that there are no other possible ethics.
I do support the idea of having free ofcharge and copyright free computing systems for the public. I might not agree with the idea that corporations are evil and that proprietary has to go, but it does not mean I disagree with the need to have publicly available software systems.
So, the latter point is also ethics. It is simply not the extreme position that Stallman opts for. In my article I write about free software as a moderate philosophy:
So, I think my usage of Linux has a philosophical component to it, definitely.