The Real Question
You know what? The OP is actually kind of on to something.
Why is it so wrong for someone to refuse to pay for a company's services or products if they don't like that company for legitimate and fundamental reasons? If you don't like Microsoft's business practices, monopolistic tactics or whatever, you should stand up for what you believe in. You should not support Microsoft financially by paying for any of it's products or services...irregardless of what good products they may and actually (reluctant to admit) occasionally do have.
The same can be said of Walmart. They may have cheaper prices than other stores and are conveniently located near where you live and/or work. However, if you don't like Walmart's business practices, how they treat employees or distributors and what happens to smaller/independent businesses because of them, you should stand up for what you believe in and not buy anything from them.
Let me give some analogies. Note: These are extreme examples meant only to illustrate a point.
1. If a company bought slaves and used them to manufacture a product and sell it to you for 1/3 the price of every other competitor, would you buy that product from them because it's a good product and so much cheaper? If you disapprove of slavery yet still buy that product from that company, you are essentially supporting slavery, yourself.
2. Would you buy a blood diamond knowing that many people were killed to obtain it? Do you justify it by saying that the blood diamond is cheaper than other diamonds of equal quality or even of better quality than other diamonds....ingnoring the human deaths associated with it?
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I think the OP didn't clearly say what he really wanted to say...but I could be wrong. This has nothing to do with being a Mac/Apple fan. Let me try rephrasing his question:
For all those people who say that they hate how Microsoft uses their size and immense cash reserves to buy themselves into markets, how they use anti-competative practices to gain an unfair advantage over other companies, etc., why do you help them continue doing so by purchasing their products and/or services?
The debate should flow from there.
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I think the OP is trying to uncover why so many people seem to be so hypocritical at times. Along with the fact that most people don't even realize it.
A lot of people speak out against a company's business practices yet they keep buying products from them (It could be Microsoft...or it could be any other company). Why? Because they say that they like some of their products or those products cost less than the competing products? When it comes down to it, a lot of people don't put their money where there mouth is. They only truly stand up against something or for something when it is economically convenient for them.
It's not just business, it could be other things in life... People speak out against a politician but they don't bother going through the effort to vote for someone else....or even voting at all. Or...people say how the environment is important to them but they keep buying the gas guzzling cars, wasting electricity, don't use more environmentally friendly products, don't live a more sustainable lifestyle,etc.. The examples can go on and on.
This isn't a debate about choice or buying the products that are good for your purposes. It's a debate on why if you say that you don't like something, do you turn around and continue to support it?