I can see why neo-pagans and heretical believers in sola scriptura might believe in flat earth, but it makes no sense for traditional Catholics to reject the traditional belief of Catholics that the earth is shaped as a sphere.  

Although spherical earth was accepted for most of the Church's history, it was never taught de fide so one might be able to make a science argument for flat earth if there were some evidence for it.  Trying to make a religious argument, however, is absurd.

The idea that Catholics believed in a flat earth at any time past the patristic period comes from anti-Catholic propaganda. It is true enough that views were split on the topic in the first centuries of the Church, but eventually a consensus emerged among Catholics that the earth is a sphere.   St. Bede, writing around 700 AD, clearly taught this and his works were spread throughout Christendom with no opposition.

As the Catholic Church sponsored university system arose, all students were taught the earth is a sphere.  Every Saint, Doctor and Pope educated this way believed the earth is a sphere.

How can people who call themselves traditional Catholics pit themselves against the beliefs of our fathers in Faith this way?

But spherical earth has not been "taught" either.  Yes, it has been widely held by Catholics for many centuries, but on scientific grounds.  Just as indeed the Church has never taught flat earth, the Church has not taught spherical earth either.  You appear to be mistaking widespread belief regarding a matter of natural science with Church teaching.  Really, the farthest you can go is to say that Catholic have not considered spherical earth incompatible with Scripture.

So, Ladislaus is a Flat Earther?  Why am I not surprised.