By default, Lemmy allows downvotes globally. However, when a server disables downvoting, it is similar to using a feature that is usually reserved for enterprises and very small, non-federated communities.
If a user prefer to not see downvotes, they can disable it by his favourite client settings, but the rest of the community should not miss this functionality for the pleasure of few users.
Forced positivity is toxic positivity.
Removing an interaction choice from users can only result in lower quality user interaction.
Removing the capacity for downvotes harms the community.
Before there was no voting, just conversations. Scoring interactions is toxic.
So your logic is that since we already have some toxic we should just go ahead and make it more toxic?
Make it less by removing downvotes, at the least.