The fact that photons don’t have to hit a magnet in order to become polarized was discovered by Michael Faraday in 1845. By passing visual light through a magnetic field, he observed polarization. This is what we call the Faraday Effect. It proves that there’s a direct relationship between magnetism and light.
The Faraday Effect can be used as supporting evidence for the position that magnetism is a form of polarized light.
When photons are polarized so that they spin along the same axis and with their positive and negative orbs facing the same way, we have magnetism.