Wine is not especially bad for you. In fact, it has many benefits. The bigger problem is wine or alcohol consumption.
Drinking is an integral part of our culture. We cannot get by any social event without drinking. Sometimes, we drink more than we should, and that's where the problems start kicking in. If you consistently have no more than one glass of wine each day, you would not be doing a huge disservice to your body.
On the other hand, many people feel that regularly consuming alcohol gradually weakens your self-restraint. There's another factor at play here as well. Over time, your alcohol tolerance level increases. You would then need more alcohol to feel the same buzz. This explains why alcohol consumption increases gradually and unnoticeably for many people.
To put it in simple words, wine is not bad for you. Too much wine is bad for you. The problem lies in the fact the boundary between just enough and too much is often blurred, and we overstep it very frequently.