ZeroJunk, eBay doesn't stay out of any other legal market I can think of. It's a whole different ballgame.
You could, in theory, assemble all the hardware and many of the chemicals you would need to start a meth lab via eBay.
You could buy adult toys via eBay.
You could buy The Anarchist's Cookbook, via eBay.
They don't choose to avoid controversial items, in general; they don't choose to avoid potentially dangerous items (you can buy used cars, ATVs, and motorcycles via eBay).
I had a friend who used to sell bar supplies from bars that either went out of business or were renovating, via eBay. I don't see eBay worrying about liability from unlicensed alcohol vendors purchasing vats, taps, etc. They allow all that to be sold.
eBay made a conscious decision to disallow guns, specifically, and they were pretty heavy-handed about it when they made the decision.
So you can buy from eBay if you want; heck, you can buy the gear to set up both a meth lab and a bar from them if you want, and cater to anarchist explosive makers who bought their know-how and some of their supplies from eBay, if you want.
Me, I won't support them.