I had no idea who he is, and that he is competing with Twitter. I would have welcomed a disclaimer about his conflict of interests somewhere in the post.
Things are going to get very tiresome if everybody is going to be expected to preface every published opinion with their entire background so you can decide whether their argument has merit without reading it.
I mean, it's certainly not illegal, and one could argue that it isn't even unethical. But it's definitely in bad form. Rude. Vulgar.