People need some perspective on "max." If Kevin Love signed a 4-year max contract with the Celtics next summer, based on current cap projections, he'd be tied for the 12th highest salary in the NBA with anyone else who also signed such a contract next summer (Aldridge, Gasol, maybe Rondo); and tied for 3rd amongst power forwards. The following year he'll be in the 15-20 range, and maybe outside of the top 20 depending how crazy spending gets with the new TV deal, no higher than 5th amongst power forwards, behind Bosh, Griffin, Aldridge, and Davis for sure, and maybe behind Horford, Ross, and Henson pending salary cap craziness.
At most Kevin Love would be paid on the high side for a year under that scenario. After year 1, he might become underpaid by comparison.
Offering Love a 4-year max should be a no-brainer for Ainge. Unfortunately, Love likely would not accept such an offer.