A bit of analog low-pass filtering and electrical hysteresis definitely helps reject EMI - but you shouldn't use these alone to do debouncing as if you do, you

A bit of analog low-pass filtering and electrical hysteresis definitely helps reject EMI - but you shouldn't use these alone to do debouncing as if you do, you introduce substantial latency for both up and down transitions. The (very simple) software algorithm described above gives you both low latency and complete resistance to bouncing. Combining the two is a complete solution.