If they accept generics, then there is an implication that the language design isn't infallible as a result of being written by Rob Pike, and then the whole house of cards falls down as people start clamouring for things like real exceptions.
Yeah they haven't done it yet, and might still never do it, to save face. What could have been a simple 1.0 missing feature has been politicized into Go's defining feature/mistake.
There is nothing political about it, and speaking as someone on the inside it is simply ridiculous to think of it that way. What these real proposals show is that a lot of sincere effort has been spent by members of the core team writing, reviewing, and debating generics proposals over a span of multiple years. Ian only recently felt comfortable releasing them publicly, and so here they are.