They way OP is attacked in this discussion is shameful.
Even when what he was told was incomplete or incorrect, there is no reason to mock someone so harshly for sharing what they consider New Information.
I work as an audiology assistant at a major university hospital in the Netherlands, where I spend my days measuring patients hearing loss, indexing their tinnitus levels, establishing speech recognition scores after cochlear implantation etc. etc.
A Google search will tell you that ear defenders struggle to attenuate more than 30dB SPL on average reliably. They encompass the ears but rest on the os petrosum, the bone behind the ears in which the cochlea is molded.
Ear plugs, of any make, wil attenuate SPLs up to 25-30ish dB, with a bonus for blocking the auditory canal (the shape of the auditory canal boosts volume around 2k Hz -3k Hz).
Together, at most 50-60 dB of attenuation is achieved. This could be comparable to hushed or polite conversation levels. Sound louder than that will make your head function as transducer and when the skull vibrates, so does the cochlea, making it send that information to your brain and you hear sound.
When this attenuated sound level reaches intensities that causes fatigue, it can damage the cochlea just like pressure through the auditory canal would.
Now infection. Ears require sufficient clean air to stay healthy. Closed off for too long, temperature and moisture may rise just enough for fungi or bacteria to flourish in spite of you earwax trying to hold them at bay. Keeping your ears and sinuses airated helps against festering and inflammation (hence the eardrum tubes for chronic sufferers).
I hope you all read this in sir David Attenborough's voice.