Allah says in the Kitab al Kareem: Indeed, We sent down the Torah, in which was guidance and light. The prophets who submitted [to Allah ] judged by it for the Jews, as did the rabbis and scholars by that with which they were entrusted of the Scripture of Allah, and they were witnesses thereto. So do not fear the people but fear Me, and do not exchange My verses for a small price. And whoever does not judge by what Allah has revealed - then it is those who are the disbelievers. [5:44]
What clearer hujjah do secularist "Muslims" need to see that they are on a path of kufr?