Out of all the groups unhappy with President Barack Obama’s budget proposal, which was released a week ago, perhaps the angriest are people within his own base.

Within his budget proposal are cuts to both Medicare and Social Security, two popular entitlement programs that are particularly dear to liberal Democrats. The most controversial proposal in the budget would tie the growth of Social Security benefits to a slower rate of inflation, known as “chained CPI.” Minnesota Public Radio reported that if enacted, chained CPI would save roughly $130 billion over 10 years. MPR also reported that on Thursday, members of the Congressional Progressive Caucus spoke out against the Social Security cuts, appearing to be surprised and feeling betrayed.

Obama likely knew how his entitlement reform proposals would anger the liberal wing of his own base and probably planned on it in hopes of coaxing Republicans into supporting additional revenue increases. Regardless of the motives, members of both parties should be supportive of his entitlement reforms, despite how politically unpopular they may be. In order to ensure a bright future for the next generations of Americans, federal expenditures on Medicare and Social Security must become more sustainable.

In exchange for the reforms, the budget calls for much needed additional spending on infrastructure and early childhood education. It also includes several revenue increases, including the “Buffet Rule” which with some exceptions would impose a minimum 30 percent effective federal tax rate on people with incomes above $1 million.

Overall, Obama’s budget is a good mix of bold but necessary policy reforms, revenue increases and new investments. It has received criticisms from both sides, which is a good indication that it should be taken seriously.