A lot of people just go ahead with the "telemetry=bad" message + critique of telemetry in general without even taking a look at the actual proposal[0] (which has some important points regarding collection frequency, data shared, and architecture). Not saying there should be no critique, but blanket statements that often criticize aspects that are irrelevant here don't help.
They're really trying to approach this in a way that, to me, is as reasonable and transparent as effectively possible (yes, I'm on the side of "opt-in telemetry doesn't work because of the majority of people who don't care either way; won't turn off if prompted, won't turn on either", so being opt-in is in fact unreasonable to me).
The Go toolchain already in a sense "calls home" by default to the Go module proxy hosted by Google.
Anyway, it's open source, they're the maintainers, it's up to them, while if you want, you can fork it. Telemetry is immensely useful to understand what features or technical improvements are worth prioritizing to benefit the actual average user the most, and not just the vocal minority. Telemetry being opt-in breaks this by once again prioritizing the vocal minority that turns it on.