An opposing point of view to hunting messing up the ecosystem is this:
Throughout history, the population of human beings on this planet has increased steadily. In very recent history, the rate of increase has been quite rapid. As a result, humans have found it necessary to destroy wildlife habitat in order to build homes and cities to accommodate their growing numbers.
Until quite recently (the last 50-75 years) the killing of what were considered dangerous predators such as wolves, bears, and mountain lions, went hand in hand with man's move into former wildlife habitat. It was though that such animals might attack humans, so they were killed.
As a result of the combination of the reduced number of predators and the reduced amount of habitat, the population of animals such as deer has risen past the point of carrying capacity of the land.
If these animals are not hunted, their numbers quickly grow to the point that they exhaust the available food resources, and they begin to suffer and die of starvation and disease.
Therefore, hunting has become a necessary means of population control. Unless mankind is willing to reduce it's own population, to stop rampant outward growth of cities, and to reintroduce predators into the ecosystem, hunting will always be required as a means of population control of wildlife.
What I have typed here are my own words, composed just now, and not copied from anywhere, so feel free to use what you wish.