>>> Without a universal point of view, "semper et ubique et ab omnibus" ethics seems
>>> to be unachievable.

>> In practice, a universal point of view means silencing the opposition.

> I wouldn't say "silencing" but "assuming that the opposition is wrong".
>
> This sounds less bad than it actually is. Relativism can be very dangerous.

It's instructive to think about morality like biodiversity, subject to
evolutionary (i.e. context-sensitive, economic) forces. For example:

- There currently exist a variety of (changing) moral stances that have
succeeded in navigating a complex world over a long period of time.
Perhaps another set of stances could navigate the same world? We can't
know since we can't reprogram the people's minds to have different
morals, and even if we did it would no longer be the same world.

- Since the current moral stances prevail there must be something that
works about them, just as some plants thrive in many regions of the
world. This is where one would look for universals. However, this in
itself does not prove that they are optimal for any given environment,
and the findings may be disappointing: complex creations tend to adapt
to their environment in some way. It may simply be that two things that
grew in the same environment have adapted to each other with limited
relevance to other environments. And what is humanity ultimately? Often
we define it by our most exceptional works and people. It may be
possible to arrive at a morality that produces the rule but cuts out the
exceptions (both the best and the worst, perhaps). It may then turn out
that the rule's long-term thriving depended on the exceptions.

- Transplanting a new moral stance into a community is like
transplanting a foreign species. Perhaps it will wither; perhaps it will
find a niche or even thrive; perhaps it will overtake the native moral
stance and become the new normal. Whether it is good for people, will
vary. It tends to be unavoidable that there are winners and losers in
such situations.

- If one really wants a particular stance to prevail, that can always in
principle be done with sufficient force, just as one can remove native
species from an environment and plant new ones. However, humans are
difficult to control in large groups and for long periods of time. Our
views are prone to divergence. In practice, homogeneity may only be
possible in environments so simple that we don't want to live in them.

As for relativism, the opposite poles of moral objectivity (other people
won't take our advice for long) and nihilism (we won't even take our own
advice) are not stable so we live in between. One can go rogue and make
one's own rules, but morality mainly matters in relation to other people
and they won't tolerate large deviations from their norms so some kind
of compromise has to be struck. A society full of people making these
compromises and we get politics. Historical events tend to shake things
up so that conservative or liberal views are in vogue at any given time,
but those views arose as reactions in their particular environment and a
society may have a pattern of cycling between them.