To start, "I like rain" is a factual statement derived from your opinion, not an opinion itself. So let's change it for "rain is good":
> If you think rain is good because it waters your garden I'd hesitate to call that opinion because you have a factual reason.
> If you think rain is good because it sounds pleasant that's an opinion.
You're making distinctions that don't exist.
Thinking rain is good because it waters your garden is based on the fact that it will help your garden grow.
Thinking rain is good because it sounds pleasant is based on the fact that you enjoy the sound of the rain.
Both of these ignore counter-factuals. Sure, you think rain is good because it waters your garden, I think rain is bad because I live at the bottom of the hill and all that rainwater frequently floods my house. I think rain is bad because I dislike the sound.
Your opinion is based on the fact most relevant to you, my opinion is based on the fact most relevant to me. Choosing which facts are most important is a personal choice that results in an opinion. They're all opinions! To finally bring the thing full circle:
> But Facebook supporting marketing because they make more money with marketing can be a verified fact
It is an opinion supported by fact. A Facebook exec could make the argument that they could make more money by dropping advertising and instead charge a monthly membership fee. There are definitely fewer facts available to back up that opinion but it would still be a valid one.
