Respectful disagree. I look at sports betting in a similar light as poker.
The correct play doesn't always result in a favorable outcome. When playing poker if all the money goes in preflop and you have AA vs KK, and your AA loses, the play was still correct even though you lost. The theory proves out because if you put your money in majority of times with +50% chance to win (ignoring rake/juice), in the long haul you'll be a winner. I believe a similar theory is in place in sportsbetting.
In sports, if you see a line of -7.5(+100) and you know that it's a winner +50% of the time, you would bet it. While you may not win, it's still the correct side.
People struggle with the theory because the "correct side" cannot be mathematically proven, Also, with many sporting events a reasonable argument can be made for either side being the "correct side" due the strong accuracy of line setters.
I suggest that you watch events with a more objective view, rather than just a winning ticket and losing ticket.
GL