You can both think cryptocurrencies are a stupid idea and believe that introducing payments into Signal is a bad idea for other reasons. Your assumption that on

You can both think cryptocurrencies are a stupid idea and believe that introducing payments into Signal is a bad idea for other reasons. Your assumption that one belief is simply a fig-leaf for the other is not justified. Based on my personal experience, people who are serious about cryptography from a public-policy perspective are likely to have both of those opinions.