Even if your number is blocked, can't you still leave voicemails? If so, OP should text back to call him a coward and a bigot for thinking that his opinion is worth more than his brother's simply because of their different political views. After the brother blocks him, OP could make it a regular habit to call his brother and leave redpill-filled voicemails on his brother's number. That way, OP get to have fun, his brother comes out looking terrible to their family, and if the brother actually listens to the voicemails rather than deleting them, he may gain enough insight to eventually research the claims on his own and wake himself up from the propaganda.

Best case, OP wakes his brother up from the programming and gets him to open his eyes.
Worst case, OP's brother stops spewing MSM talking points into OP's ear/phone.