Well, whenever you produce goods, there are production costs associated with that regardless of where your materials are sourced from. Yes, producing glass from recycled waste requires energy, and, therefore, can create pollution. But when it comes to assessing environmental impact, the big picture needs to be considered. That you are eliminating usable resources from a waste pile in of itself is a good thing. Using post-consumer waste encourages less exploitation of virgin resources in the pipeline as well, which is also a good thing. The energy actually used to manufacture recycled products will depend on the producer.
At any rate, recycling is a small part of the phrase, and it's listed last for a reason. The best thing to do to reduce mismanagement of natural resources and improve sustainability is to reduce - to not consume needlessly in the first place. The second best thing to do is to reuse - to make use of produced products that are already available or repair things that are broken instead of insisting on something new. These two should be emphasized an order of magnitude above recycling, and it's why they are listed first. If you want to live green, the number one thing you should do is consume less and consumed used whenever possible.
