I wouldn't say that volunteer firefighters are "hated" per se, but they do not receive the same level of respect. It's like comparing a soup kitchen volunteer, to a full-time charity worker. Yes we appreciate your intent but at the end of the day this isn't your profession so you aren't making it your priority to stay on top of procedures, training, equipment upgrades, etc. If every volunteer routinely checked fire service news sources (they have fire service news apps now, for heaven's sake) then they'd be more informed and earn more respect.
Not hated, just not respected - as much. Volunteers don't train constantly, or are aware of current events/techniques/policies/strategies/etc... At the very least, anyone participating in fire service or emergency medical services, should keep themselves updated onfire service news so they're actually helpful and not just getting in the way of professionals.