Puppies and kittens are skinned alive for their coats and then left writhing to die.
You cannot compare that to a cow being humanely killed and then its hide being removed.
Fur removed while the animal is still alive is a whole 'nother issue. I'm talking about regulated fur-farming in which the animals are electrocuted before their fur is harvested. This method of killing is endorsed by the law as humane, just as stunning-and-bleeding of cattle. The skinned bodies are used for fertilizer, animal feed, or dissection classes - generally not thrown away. This is a prominent source of popular fur (mink) in North America.
There are people (myself included) who feel that "humane slaughter" is an oxymoron. Not everyone agrees on that. But if you think it's wrong to kill an animal (ie. to deny it of an obvious desire to continue living) for spurious reasons (eg. for its fur, which you'd still be able to live without), I think you need to be consistent and equally vocal about the use of leather.
You bring up an excellent point that leather alternatives are often not feasible or environmentally unsound. I would counter that we have not yet had sufficient interest in research to develop practical, sustainable leather alternatives. There are some decent alternatives out there, but more consumer interest would generate more development.
As to soy production in Brazil, direct-consumer soy products (soya milk, tofu, etc.) account for a very small fraction of soybean production. The same is true in the US, where soy is a more conventional crop (the US imports very little soy, but Brazil is a major exporter of soybeans to the EU). Where does 90% of soy produced worldwide go - ? According to
this report (and what my general understanding is) it does straight into industrial animal feed. Even with rising consumer demand for "healthy" soya foods, the growth of animal agriculture exerts a far greater influence on soybean production, even in Brazil.
It is also worth considering that, pound-for-pound and calorie-for-calorie, it is more efficient to eat the soy ourselves than to first feed it to a cow, allow the cow to convert it to muscle and fat, and then eat the cow - we could see equivalent nutritive yields with less land-use (in the Brazilian rainforest and in our home countries) if we ate soy directly, rather than indirectly via an animal.
There are many issues at play here (and in the fur-leather-meat-milk debates), and they strike at a lot of deeply-held beliefs about our moral orientations towards nonhuman animals. My initial point was only that I think it hypocritical of PETA to vehemently protest the use of fur but remain silent on the use of leather (instead of encouraging consumer demand and development/research into alternatives). Yes, fur is a luxury item, and yes, it serves little practical purpose in temperate climes - but if one believes that fur is wrong
because it is wrong to kill an animal for something that isn't life-or-death essential (which I believe is more PETA's orientation) then leather is just as bad.
The heart of my opinions stems from the fact that I see no reason to make a distinction between a dog and a cow when it comes to taking a life for hedonic satisfaction (meat being tasty/convenient/traditional). Inasmuch as a cow and a pig and a chicken and a dog all display a desire to continue living, it seems wrong to me to deny them that. Others will disagree, but that's where I am.