Then it's dismissal due to somebody's ignorance. If you are talking to this person, who knows nothing about games - why can't they ask you to elaborate instead of assumptions? I feel like people are playing games with each other instead of just talking and being genuinely interested - and that is truly childish.
I agree that it shouldn't be the only thing you do, but if somebody dismisses your interests while they know almost nothing about it - then good riddance. Reading books is media consumption and a very broad statement as well - is that a non-answer too?
Also I bet it's not like these people are curing cancer or feeding starving orphans in their free time.