Saying it is no support for higher prices is different than saying it places pressure on the price (downward).
Another way to look at it. If the block reward had always been 25 BTC would we still be at $2.x right now? What if the block reward has been 1 BTC or 1,000,000 BTC?
Also as others have pointed out difficult =/= reward. Rising difficulty affects miner profitability but makes no change in the daily supply of new coins. Falling block reward may also affect miner profitability (although I believe difficulty will continue to decline over the next year) but it is different in that daily supply is reduced.