The full Ryan quote that starts at the bottom of the OP:
Here's what the new law will do. We make no changes for those currently at or above age 62. This reform affects only younger military retirees. Right now, any person who has served 20 years can retire—regardless of age. That means a serviceman who enlists at 18 becomes eligible for retirement at 38. The late 30s and early 40s are prime working years, and most of these younger retirees go on to second careers.
That is not an unreasonable change. In law school I new several folks who had done their twenty and retired from the armed forces; they were all in their late 30s or early 40s. At least one of them went on to a rather lucrative career. Someone like that has a lot less of a need for military retirement benefits than does a retiree who is over the age of 62. This is essentially the same thing that Ryan proposed for starting to get social security back on track: reducing benefits for those under retirement age but not for those who were at or near retirement age and therefore not in a position to replace the lost benefits through work.