The simple answer to this question is no, cutting bred will not significantly blunt your bread knife as long as you are using a proper bread knife.
A proper bread knife will have a serrated edge, a blade with lots of little teeth on it. This allows you to cut through the crust by working almost like a saw, with each tooth getting a chance to cut on each side of it before slicing easily through the softer dough under the crust.
There is science behind this, using a serrated knife will increase the amount of force used to cut the bread as more force is concentrated at each serration or tooth.
Obviously if the bread is stale or very hard then you do run the risk of damaging the blade teeth and serrations by perhaps bending a tooth or breaking the tip of it but that is the only real risk you have unless the knife blade itself is very weak.
Over time and with use, any knife will loose some degree of it’s edge and this applies to bread knives as much as any other kind of knife. It can be difficult to sharpen a bread knife due to the serrated edge but it can be done by using a sharpening tool such as a ceramic sharpening rod.
However you should only sharpen on one side of the blade. A good quality electric sharpener may also do the trick. You can of course use a sharp non-serrated knife to cut bread but it will be far more difficult to break through the crust and it will not slice the dough as easily, neatly or sharply.
As a result your slices may have a more crushed and squashed appearance, especially if the bread is very fresh. A non-serrated knife used regularly on bread will loose it’s edge much quicker then a serrated blade,