"Go outside" (commonly paired with 'and touch the grass' or 'and pick up a football') is a phrase that's used against a person when they're defending, promoting or doing something that's
illogical, weird, or immoral. The phrase itself suggests that the person in question is closeted or dissociated from reality and that they need to go outside and step away from
the internet in order to realize what they're fighting for/doing isn't
a big deal, is gross, or just completely stupid.