Stereotypes about people from madesh created by the ones living in hills and mountains, calling them "madeshis", treating them as second-class citizens has nothing to do with what is going on in Nepal right now. It is a completely different issue. The problem right now is not social, but political. Madheshis want the entire south of Nepal to be one single state. This is absolutely not necessary if their concern is representation and recognition. They want a bigger representation in political landscape because they represent almost 40% of nepalese population. But this is ridiculous in a federal state. Every state should have equal representation. Imagine California, New York and Texas having a much bigger representation in american politics than rest of the other states because they together make almost 30% of the american population. Isn't one of the goals of a federal state to secure voices of minorities?
Now it's been clear why madeshis want this demand. They are closer to India in every sense or at least their leaders are then to Nepal. So if we let 40% of nepalese politicans to be from Madesh, it will become very easy for India to use these leaders to extort whatever natural resources we have in Nepal. Nepal and Tibet have many rivers, thanks to the melting ice from the Himalaya. With the invasion of Tibet, China now controls all the water from rivers on the northern part of the Himalaya, and India wants to do the same with the rivers that flow from southern side of the Himalaya. It's all about water as with increasing Indian population, from drinking water to irrigation to hydropower, water will be even more scarce, thus precious.