So basically he is skeptical about Ethereum and particular Ethereum mining because he thinks its not helping anyone, just like Bitcoin. What do I tell him?
So basically as I would explain it, Ethereum is a new blockchain that can not only store transactions but also contracts using all sorts of programming languages via DAPPs (using EVM / Ethereum Virtual Machine Code). The mining process helps to validate those transactions on the blockchain. So the energy we use to mine is not wasted, it is used to create a secure network of contracts that are decentralized, stored on many computers (P2P).
What other arguments can I make to convince this person that miners are doing something valuable and not just wasting their time?
Also, how exactly does a mined block help secure the network? That part I have never understood myself, is it because we are all storing a copy of of the block on our computers? Or how exactly does it make it 'secure' (in simple words)?