As someone who has a CS background who wanted to work in front-end, I think a big portion of the "looked down upon" piece comes from an older era where front-end just meant HTML and CSS. Since there isn't much logic to HTML or CSS, it was looked down upon as easy from people with a CS background who generally gravitate towards the backend.
Now that the front-end is more robust with arguably just as much logic on the front-end, the thought is shifting. In addition, some people just don't like handling the GUI layer. For the back-end, dealing with the GUI layer is their least favorite part. So if you have a CS degree and you want to tackle the front-end, you could be one of the rare few who has the technical chops to handle this new world of front-end complexity.