Overpopulation of any species can cause ecosystem collapse, even without their obvious starvation or encroachment. Overconsumption of feed species (plant or animal), destruction of habitat for other species through overcompetition, runoff characteristic changes causing erosion and overfilling of streams, which has run-on effects for watershed health that affects both our drinking water and our waste removal systems.

For an extreme example, check out writings on the reintroduction of wolves to Yellowstone, specifically how the physical environment rebounded based on decreasing overpopulation of non-predatory species. i.e. deer: https://www.nationalgeographic.com/animals/article/yellowstone-wolves-reintroduction-helped-stabilize-ecosystem

The lack of a predation force on grazing animals like deer in suburban areas is a genuine problem for the local ecosystem - though arguably comparable to other issues like grass-monoculture and non-organic runoff.

Despite the commenter you wrote to, Maryland's gun laws are pretty pro-hunting on the whole - little restriction on the types of firearms used for and useful in that activity, and well more than half the year is some sort of hunting season at a state level. The problem is more HoCo-specific, which prohibits private discharge of a weapon at basically all times and has no hunting grounds at all, as far as I've found. The county does two culls a year with hired sharpshooters, but it never quite seems to be enough to really curtail the population in safe bounds; I'd be curious to see them study private-land hunting in-season in the western part of the county, and also study bowhunting in denser areas.

At the end of the day, the problem is that nature doesn't exist outside of human development, but despite it. We're collectively generally pretty bad at actually examining how we fit into ecosystems, treating them like problems to be excluded from our communities rather than complex systems that we're trying to fit ourselves into. Modern life is pretty good at scaring off predators, so instead we have to deal with the prey - we've become the apex predator of the local ecosystem, and failing to act it is a bit like taking the wolves out of Yellowstone.