Im more into population control of animals that [censored] up ranchers land. but thats just me.
No. That is equally wrong. The wolves of Yellowstone National Park are damned near extinct because of that. And when you think about it, they were on that land before we were. We are the intruders. And they only go after fenced-in farm animals when other resources are low, so if we kept the prey populations in stock they would likely never bother with the cattle anyways. Or, I dunno, reinstate the watch dog. Put some of them pooches we BRED for work BACK to WORK.
Exactly. Diseases keep populations from reaching the carrying capacity of their environment. Particularly true of viruses, who only infect and do nothing else, since it is how they reproduce. However, in the case of bacteria, they are actually not maliciously seeking you out to destroy you. In most cases, they are merely trying to survive in their environment (you) which sometimes causes some nasty side effects for you. Myxococcus Xanthus however actually hunts down cells... so that's a different matter.
But for most bacteria they are typically natural bodily flora that thrive in/on your body, and only cause disease because of an immune system 'hiccup' that causes you to react to their biological products, and hence get sick. A virus' ultimate goal is to blow up that cell and make more of itself. A bacterium's ultimate goal is simply to survive, and that may/may not require the death of other cells.
Therefore, eradicating viruses would be beneficial, but not bacteria. Our normal body flora like E. coli and S. aureus actually help stave off infections through resource competition. But regardless, they are key to maintaining a population ceiling, and our fight against them reveals the consequences of their removal. Note how we are running out of space.
Every organism has its own niche, no matter how small, vile, or subtle it may be. Removing even a single celled organism could have repercussions on an ecologically deadly scale.