Trump has been courting controversy in public speeches since he announced plans to run for the White House in June (15), but he came under fire on Monday (07Dec15) when he called for Muslims to be banned from entering the U.S. following recent terror attacks.

Simmons, who has previously spoken out against his longterm friend, has now posted an open letter to Trump on, insisting the politician could become the Republican presidential candidate by being the "amazing friend" Simmons' knows, rather than using hateful remarks to garner easy votes.

Following a passage about their 30-year friendship, Simmons writes, "You are a born leader, who is set to possibly win the nomination of your party, but don't compromise what I know is in your heart to do it. You are a generous, kind man who has built a career on negotiating deals where everybody wins. Now, you seem like a one-man wrecking ball willing to destroy our nation's foundation of freedom.

"Stop the bulls**t. Stop fueling fires of hate.... You have been many people's champ in the past, but now you are becoming a major embarrassment. I know the cheap seats are easy to play to, but you can get them just by being the man I have known for nearly 30 years...

"You are trying to be president of a country built on religious freedom; remember that the next time you discuss the beautiful followers of Islam... I wish you good luck on your path towards the White House... I will be campaigning rigorously against you. But if you win, I might still accept an invitation to your house to straighten you up every so often. With love, Russell."