If it really repulses you to use animal products then you shouldn't use them at all, from any source, whether that means buying them new or second-hand. I think if you have labelled yourself an animal rights kind of person, and want to be known that way and want to set an example, then it is bad for your cause for people to know you use these kind of items, no matter where you got them. If you speak out heavily about these kind of things people will be watching what you do and will be very critical when they think your words and actions don't match.
However...if you don't open yourself up to such scrutiny, and choose to live your principles instead of yakking on about them, then you can look at things a little more objectively and from different angles where the answers are more personal and right and wrong isn't so easy. It is very true that demand creates the supply of these items...if no one wanted leather, cows would not be killed for leather. But your dollar doesn't speak nearly as loud in the secondhand market as far as creating demand for that item and keeping the manufacturing processes of these products alive. If an animal has already died to be made into food or any other item, I think the saddest thing is that the item would be wasted. So really using that item to its fullest potential is, my opinion, the best way to honor the life of that animal that died so those boots or that jacket could be made. Refusing to use that item doesn't un-kill the animal. And yes it is more eco friendly, keeping unwanted items in circulation and out of the landfill...which is an animal rights issue in itself as we encroach more and more on their habitats to find places to put our trash.