you can quite easily get testicles in this country (UK), just ask your butcher. It might depend on wherabouts in london you live, but it's an eastern delicacy, so where eastern food is available eastern culture is there too. It's like iVersa says, its only weird because we have been brought up believing it.
I haven't had any penis though, and I think i would be a little scared asking in case of any hilarious misunderstandings that may take place.
Unfamiliarity of food breeds 'eww' factor among many. It doesn't mean that it's not good. To me, for example the majority of 'traditional' American food is familiar to me but it is subpar as far as cuisine goes, while far more obscure foodstuffs which (e.g.) the average fish and chips-loving Englishman would go 'urgh' at presents me with a much more intriguing food experience. And arguably there are plenty of things in the Western larder that would cause the average Far Eastern to go green just by thinking about it.
The problem with this is as outlined in the article, not specifically the penises (penii?) and the fact that looking at someone chowing down on one brings tears to my eyes but the Chinese penchant for scarfing down an enormous number of endangered species in the name of delicacies.
You've only got to look at the Japanese to see how much devastation one group of guys can cause to the ecosystem with just a love of food. However when like the Chinese your diet encompasses practically everything that moves and that specific bits of endangered species (the loss of which usually kills'em) are of great interest as high-end food, with the rapidly increasing prosperity of the Chinese you've got a serious problem in the making.
Some species such as dogs are enjoying reduced popularity as people gradually adopt more western living mores and apparently dogs on a plate are a bit naff these days. But that's really only among the younger people - the seniors still regard rare, endangered food as aspirational ostentation.
It's not like all Americans try all 'Western' delicacies and all dishes... same w/ Asians and Chinese. We don't eat everything. My parents and I have never had dog-- and I know that my mom and I haven't had blood (either as a cold-cut dish or in a cocktail). I haven't asked her about penises and testicles, but I'm fairly certain she hasn't had any of those either (nor have I).