No, people with more seniority should not be hired over younger people, because people should be hired based on their talents. Older isn't always better. In fact, older is often more set in their ways, and not open to new ideas. The person hired should be the best one for the job, plain and simple.
In my opinion the discrimination over age, race or religious belonging when it comes to hiring and the job market is an outdated and backwards looking model. It is important to appriciate the experience that seiors bring to the world, however we should not forget what potential and new fresh energy, ideas and much more the younger people have to offer. Each job has a specific demand and I think hiring should happen upon careful evaluation and fitting of the applicant and the open space rather then discrimination.