Great.
Problem is that the gemara [Shaabos 132b] says that not removing tzaraas is not just a לא תעשה but and עשה as well so it is really a case of עשה דוחה לא תעשה ועשה which it doesn't. So, bi'kitzur, how does the Ramam shtim with the gemara??
See the Kli Chemdah on Parsha Tazria and the Nachalas Tzvi [chelek beis] as well.