seems like you get too emotional about this, they're parasites but so are you - they take money from mugs, you take money from their marketing budget making it less effective... they try to prevent this by putting in terms and conditions allowing them to not pay and they will chose not to pay certain people
nothing in this game is 'risk free' you're naive to think so and bitching about a single bet is ridiculous, they made the right choice, you didn't get paid out... so what - move onto the next one. You're going to have to accept that you need to chalk up some losses every so often. Do it long enough and you'll find that there are plenty of other anomalies along the way from less reputable bookies not paying out on bets you've actually won (not just cancelling your free bet) though to different rules on handling various anatomies that may occur in sports leaving you unhedged.
Its a game that you can, or at least could a few years ago, make tens of thousands from - bitching and moaning about one small bet is silly. Calling bookies parasites is silly. They're there to take your money you're there to take theirs, get a better appreciation of how this all works and ditch silly moaning. If you can't even handle simple match betting then please don't move onto taking advantage of any other +ev opportunities in gambling. I'd hate to see your reaction if you got on the wrong side of a well known person at 5dimes etc.. (if anyone is interested then google some of the reviews - makes for amusing reading, the manager there takes it very personally when he thinks people have screwed him)