vegan

i think answers like this are maybe too concerned with theoretic purity and maintaining a certain label.

Having a clear message and working towards the goals of the movement is not "being concerned with theoretic purity". Words have meanings for a practical purpose, and stripping those meanings away makes it more difficult to organise.

A living being created to suffer and die for an abominable purpose and then not even used for that purpose. It’s like a mockery and just takes the complete lack of respect for life they have to a higher level. In my mind at least.

The issue here is that this is just untackled speciesistic thinking. It's not "respectful" to consume the flesh of someone who was killed, nor is it worse to "waste" the products of their exploitation.
Every human under capitalism is "created" to serve capital. It is not a "waste" if they were to die without getting completely exploited for all of their labour power to the day they die, except through the lens of a capitalist.

I mean most of them still like the taste and texture of corpses thus the booming replacement market. So it’s more like they’re forcing themselves to be vegan. Repressing their urges though the urge is still present. [...] You can’t really consciously decide to not crave something.

People like certain tastes and textures, especially things they are used to. There is no reason to give up something they like if they can have it without murdering someone. The same applies for clothing and entertainment. There are no supernatural urges or cravings, and practising a vegan lifestyle is not a stoic struggle towards noble virtues through suffering.
Changing any habit takes some time and adjustment, there is nothing special about it.

But as we know most people ‘‘quit veganism’’.

Actually, no, we don't "know most people ‘quit veganism’’. A lot of people go on plant-based diets for any number of reasons and call it "going vegan" because the word vegan has become synonymous with plant-based food in many countries (this has both positive and negative consequences, but it's out of the scope of this discussion) and is often used as a marketing term.
People quit all sorts of diets all the time. It's nothing out of the ordinary.

It does not take much investigation to find that the overwhelming majority of people who say they are "ex-vegan" have never had anything to do with the movement at all. There are some examples of activists going "ex-vegan" and it gets very publicised, but ultimately it's a very small number of people.

I don’t necessarily see his behavior as a problem as it’s not actually contributing to the industry to eat what would go to waste. Do i think he can call himself a vegan? Probably not, but I don’t really care honestly. It’s just a label.

I'm not interested in any one person, nor am I trying to be the "label" police. My take regarding this has to do with organising and how having concrete terms with concrete meanings is crucial to that process; this is not exclusive to veganism.
There are practical reasons behind the labelling of certain organisations and individuals as "TERFs" rather than just "Feminists", for example.

What really matters is the consequences of one’s actions. Which in his case don’t seem to be negative.

Like I said, others in this thread have already tackled this, so there is no reason for me to rehash it here, but in short, I do not agree that the consequences of those actions are not negative.

Ultimately, I believe you focus too much on individuals and individual actions rather than the big picture and how the movement as a whole, not individual vegans, should conduct itself.

My perspective is shaped by my experience in organising locally and engaging with dozens of other organisations nationally and internationally. I have seen many strategies from across the spectrum, many mistakes (made many myself), and many successes. I started organising first, then arrived at theory later out of practical necessity.

"Without revolutionary theory, there can be no revolutionary movement.",
"[...]practice gropes in the dark if its path is not illumined by revolutionary theory.", etc. etc.

It's not through a concern of "theoretic purity", rather a practical concern with driving the movement forward.