In his argument, Korach says the words ‘the people are all holy’ (16;3). This was part of his faulty outlook on life, for HaShem tells Bnei Yisrael that they ‘shall/will be holy’ (vayikra 19;2). In other words, Korach is hinting that it is enough to think one is holy now, but HaShem reveals the correct attitude in saying that no-one should assume they are fully holy at the present moment – we should always strive to grow and look to a time in the future that we WILL be holy. This is why Korach is from the root ‘Kerach’ meaning ice, for ice keeps things cold, static, with no movement – just like his words hinted at the dangerous idea of keeping still spiritually and not aiming to continuously grow. And ‘korcha’ means a bald spot (Dvarim 14;1) – again, where nothing grows (heard from R’ Eitan Feiner).