I think the spirit is that patents are not legitimate. Suing for patent infringement is not considered exercising a legal right, it's considered being a dick and vandalizing someones property. So this is not to be read like a contract between to businesses, but like a truce.
It might as well say "we agree to not destroy your business using dirty tricks if you don't attempt the same".
That's how Apache 2.0 and GPLv3 treat patents. The language in the React license is not symmetric like the above licenses and thus doesn't feel like it's a "screw you" to patents. Not to mention that Facebook is very patent-heavy and it doesn't feel like they're anti-patent in any meaningful way.
I'd be more sympathetic to Facebook if they declared they would never use patents to sue someone and they'd only use their patents "defensively". Of course, they'd never do such a thing even though such a statement has zero weight.
> Suing for patent infringement is not considered exercising a legal right, it's considered being a dick and vandalizing someones property. So this is not to be read like a contract between to businesses, but like a truce.
This is an oversimplification. There are plenty of mum and dad inventors who would get destroyed by large companies but for relying on patent protection for their life's work.
It might as well say "we agree to not destroy your business using dirty tricks if you don't attempt the same".
Of course, opinions on that are divided...