The issue with primal is also that since the client is geting data from their "caching" backend service, they can (not saying they do) also censor anything, not only trending. Until they don't give the option of not using their caching backend and get data from relays directly there is space for disagreement.
Discussion
I, personally, see no evil in this. Nostr, the protocol, does not censor anybody and users content is discoverable in a multitude of ways regardless of what a particular client does.