do you manage to make friends with non vegan people?

[Jebus]

We should strive to be as friendly as we can to everybody, since this is the best way to reach them and change their hearts

Most of the people most of the time, yes, but there are exceptions. Some people won't even hear your message until you attack them. Other people may listen to your message and even say they agree, yet continue to eat meat. I don't think continuing to be friendly would be effective in this case.

We have to make a distinction: Who people are, vs. what they do

Exactly. Being nice to someone while they perform a harmful act is not an effective way of changing their ways. For example, you can be nice to a paedophile but don't be nice to him while he's jerking off a 10-year old. Also, you can be nice to a meat eater, but don't be nice to her while she's eating meat.

I am still friends with my old meat eating friends, and I still enjoy their company. However, I would never bring in a new friend in my life who isn't vegan (or atheist).

[Cirion Spellbinder]

No, [axioms are] semantic [...] (the sounds we use to make words are not inherently meaningful, just become meaningful by consensus), but the concept itself is rational as long as it's coherent.

How do we know our definition of morality is consensus? How far reaching does consensus have to reach to be meaningful? (ex: cultural consensus, national consensus, planetary consensus, galactic consensus, universal consensus, etc.)

If someone with a non-consensus definition of morality derives a valid consequentialist system of morality from said definition, is his system inferior to that of the consensus definition of morality?

[brimstoneSalad]

How do we know our definition of morality is consensus? How far reaching does consensus have to reach to be meaningful? (ex: cultural consensus, national consensus, planetary consensus, galactic consensus, universal consensus, etc.)

Consequentialism based on the golden rule/altruism is about as close as you can get. There are popular concepts out there that are not coherent, though: despite popularity they fail to fit the bill for that reason.

If someone with a non-consensus definition of morality derives a valid consequentialist system of morality from said definition, is his system inferior to that of the consensus definition of morality?

Then it's not morality, it's some other coherent concept which needs its own word.

[Cirion Spellbinder]

Thank you for answering my questions so thoroughly, brimstone.

Consequentialism based on the golden rule/altruism is about as close as you can get. There are popular concepts out there that are not coherent, though: despite popularity they fail to fit the bill for that reason.

What do you mean by coherence?
Do you mean that not all definitions can be turned into consequentialist systems? If so, why?

Then it's not morality, it's some other coherent concept which needs its own word.

If we became aware of an intelligent alien species with a population greater than our own who define morality differently than altruism / golden rule, would we be rationally obligated to follow a consequentialist system based on the alien definition if we wanted to be moral?

[brimstoneSalad]

What do you mean by coherence?
Do you mean that not all definitions can be turned into consequentialist systems? If so, why?

Look at deontology, and the pile of contradictions it is. That may pass the acceptable usage test, but it fails at forming something that amounts to a useful system.

If we became aware of an intelligent alien species with a population greater than our own who define morality differently than altruism / golden rule, would we be rationally obligated to follow a consequentialist system based on the alien definition if we wanted to be moral?

The proper translation of "morality" into their language would be a different word, or, if they didn't have that concept, then they would need to coin a new word to represent it, or take "morality" as a loan word from ours.

If they happened to use the sounds of the word "morality" to describe what we would call a table, that's a different word in a different language that just happens to sound the same.
If you said "morality" in the context of that language, you would be talking about tables.

Sometimes concepts are incorrectly matched across languages and cultures and called the same thing when they don't really translate. This is rarer for simple physical things like tables, but for mythological or philosophical things it's common since they have no physical object that's easy to point to that concretely represents them. For example, mythical creatures like the unicorn, phoenix, and dragon: these do not exist in Chinese. Instead, they are superficially similar celestial creatures but with very different lore and natures behind them.
In the same way, there are attempts to translate vedic or Buddhist concepts into English which often fail or get distorted in translation.

[Cirion Spellbinder]

How do we address definitional differences between different dialects in the same language?

In the same way, there are attempts to translate Vedic or Buddhist concepts into English which often fail or get distorted in translation.

Would an English speaker have to learn to language to understand these concepts?

[brimstoneSalad]

How do we address definitional differences between different dialects in the same language?

Dialects tend to be counterproductive to the purpose of a language, unless we're talking about a set of technical words that people within a particular field need to facilitate and improve communication.

Would an English speaker have to learn to language to understand these concepts?

I don't think so. It's more that they can't be properly translated in a single word. I don't think there's anything that would inhibit one's understanding from reading the Wikipedia page, for example, which covers the history and context.