I dont think he had a problem with coming on vs Spurs. What was disrespectful was giving him the VdB treatment, and just putting him on for 3 mins to waste time. Obviously, this is up for interpretation, but I think doing this to someone like Ronaldo or Messi is not right. Any other player, its fine. Yes they are not the same player they once were, but you have to honor their legacy in the game.
I think the only reason ETH kept Ronaldo was because he knew the board did not have funds for another CF. So he did the practical thing, and what was best for the club. The best scenario would have been if Ronaldo was told to leave in summer, because I have zero doubt he would have wasted 6 months of his very last days of football, if he knew ETH considered him a sub player. Dunno if other clubs were interested, but surely a solution would have been found, if they really wanted.
I also think this Tottenham incident was just the tipping point, and that things were boiling between ETH and Ronaldo for quite some time. Sad to see it come to this, but backing ETH is the correct decision from the club. Simply a case of players and club's interests not aligning. Not the first or last time this has happened. Remember something similar happening to Berbatov/SAF in their last season(obviously a very different case).