Q: Do I need to use filters for protection?
A: Yes. Or no.
There is a great deal of disagreement about whether or not it's a good idea to use protective filters (clear filters or UV filters) with your lenses. Here are some of the debating points:
Protect the front element
Do filters protect the front element of the lens? Maybe. They'll probably protect from casual scratching, but under most circumstances, a lens hood would do the same thing. They'll probably also help those of us who are in the habit of leaving the lens cap off when the lens is rattling around inside the camera bag.
But there's no indication that a filter would provide assistance in case of serious trauma to the front element. True, there are plenty of pictures of shattered filters and stories of folks who dropped their lands and thankfully, the filter too the hit for the lens. But you don't find a comparable number of people who don't use filters who have broken front elements.
Cleaning, even if done properly, will wear away the multicoating on a lens element. In this case, having a filter will prevent wear and tear to the front element of the lens. Whether this is will happen fast enough/intensely enough to justify buying and using protective filters is a judgment call.
Superfluous glass in the light path tends to degrade optical quality, either subtly, or blatantly — for example, creating reflections.
Whether the possible protection provided outweighs the possible problems of optical artifacts and the added cost of yet another accessory is up to you.
If you do buy a filter, it is strongly recommended that you buy one that is multicoated. This will minimize the negative impact on image quality.