Accusations of gatekeeping should be accompanied with evidence of malice if they are to be taken seriously. Correcting (or, more like augmenting) someone speaking authoritatively on something is not gatekeeping. Also, gatekeeping has a social value, when used at the right time in the right circumstances. Bouncers literally keep the gate at a venue. Relevant experience in a given field is often necessary to have high-level (or in-depth) conversations about something within said field. If you have a group of people comparing sorting algorithms and some dude rolls up to offer his opinion without even understanding what a sorting algorithm is, would you 'appreciate' their uninformed and uninsightful take on something, lacking the shared knowledge of your group? Or would you rather clarify where the guy is wrong, refer him to a resource, and tell him to come back when he knows a bit more about what he's talking about?
Don't get hung up on details here. It's not about sorting algorithms. It's about 'deep knowledge' in a field needing to be shared to elevate discussion, for lack of a better descriptor.
Gatekeeping becomes a problem when it's mean, when it isn't helping anyone learn more, and when it's not protecting a culture or improving discussion in any meaningful way. Helping newbies learn from better sources is arguably gatekeeping -- it's just not considered harmful.
Now if we could do something about baseless accusations...
