If you publicly express an opinion that any particular platform is best for a significant portion of buyers, you’re effectively saying that the people who chose differently were wrong. Most people don’t like to be wrong.
And because it’s such a massive and divided market, any stated opinion will cause this reaction from a lot of people. If, for example, you say Android is best for any common set of goals, a lot of people might get upset:
Not seeing this implication requires more open-mindedness, empathy, and attentive reading ability than many people have. So no matter how much you wrap it in qualifiers or try to be constructive, a lot of people are going to be insulted if you say something good about the thing they didn’t choose — and it’ll be even worse if you say something negative about the thing they did choose.
Spot on. Thinking something is better doesn't make you a fanboy. If you can articulate well the points on which your opinion is based and can acknowledge what positive points other products have, you can still reasonably come to the conclusion that other products are inferior as a whole.