No it's not claptrap, it's not childish, and often it is well thought out criticism. The OP states quite well why - he's "doing very nicely thank you very much" at the expense of everyone else who uses (directly or indirectly - eg by buying something that used electricity in it's import, manufacture, or distribution) electricity. As someone I know put it when he had panels installed, "if they're giving away free money then I'll have some of that".
Except that it's not free. It's a regressive tax in all but name - it's specifically designed to give people who are by definition generally "not too badly off*" money. All in all, ROC, FITs etc are cleverly designed to allow the government of the day who brought one in to claim it's not a tax - though it's the sort of thing you say with your fingers crossed behind your back.
* You have to own a roof, and in general have a pot of cash to spare (unless you want to make your house unsellable by renting out the roof).
Thankfully some of the energy companies are now talking about it openly, and identifying (in part at least - they don't include the costs of mitigation for the intermittent generation) how much of your bill is going towards these subsidies.
