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.... no, but sadly there are people who rush to judgement without due cause or evidence, and seem to be quite fond of the broad blanket.
https://www.ufc.com/news/fighters-who-give-back
Its a trend that starts at the top - the UFC itself regularly raises money for good causes, most notably the Fight for the Troops events that benefit injured veteras via the Intrepid Fallen Heroes Fund.
The story has rallied support from celebs raging from Eddie Vedder to Johnny Depp. Now the UK’s premier UFC Welterweight has recently been holding benefit events - including his UFN 24 afterparty - to raise money in support of Free the West Memphis 3.
Takanori Gomi
The former PRIDE Lightweight Champion and one of Japan’s biggest MMA stars has started the Fight Back Fund, which is a relief effort for Japan from the earthquake and tsunami. The website will donate entire sales amount of all purchases to the Japanese Red Cross Society.
Edson Barboza
The UFC 128 Fight of the Night winner’s charity of choice is one close to his family and place of birth. Combat Athletes for Nova Friburgo is a nonprofit formed to raise money and support the relief effort in Nova Friburgo, Brazil, where mudslides have killed hundreds and displaced thousands of people. Many in the city, located in the mountainous region northeast of Rio de Janeiro, have lost family members, homes, belongings, and jobs in the largest disaster in Brazil’s history.
Brian Stann
He's a Marine Captain, a Silver Star winner, an American hero, an author and a rising name in the UFC’s Middleweight division. And Stann’s time outside of the cage is devoted to the charity he runs Hire Heroes USA. The nonprofit’s mission is to help military vets get back in the job game.
James Te Huna
At UFC 127, the 29 year old New Zealand native generously donated all of his fight earnings to the victims of the 2011 Christchurch Earthquake, a move which inspired the UFC to match his donation. Te Huna currently lives in Sydney, Australia, but was born in Darfield, New Zealand, which is a neighboring town of Christchurch.
Brendan Schaub
Besides winning Knockout of the Night at UFC 128, Schaub is a two-time winner of the “Tequila Cazadores Spirit Award”. The award is for UFC fighters who show integrity in and out of the cage and provides a donation to the charity of the fighter’s choosing. Schaub’s donations have gone to Doctors without Borders and the Colorado Humane Society & SPCA.
Forrest Griffin
Do you want to selflessly donate to charity and selfishly get something out of it? Good news, Forrest Griffin solved this troublesome paradigm by donating all proceeds from his second laugh-a-minute book "Be Ready When The Sh*t Goes Down: A Survival Guide to the Apocalypse." The money is going to several charities including Fisher House (offers temporary homes to the families of hospitalized soldiers), Three Square (a Las Vegas food bank), Forrest’s local church and trust fund for the 5-year old son of a deceased friend.
Rich Franklin
In 2008, Rich Franklin was named an ambassador for Disabled American Veterans a nonprofit with 1.2 million members. Franklin also supports the cause through visits to VAs and military hospitals, public service announcements and frequent donations.
Randy Couture
Before he was a member of the UFC Hall of Fame, “The Natural” was a member of the United States Armed Forces. To give back, Couture started his own nonprofit, Xtreme Couture GI Foundation, which raises money for soldiers wounded in action and their families.
To name a few. 
.... in a bushel. Have you proven, as the OP states, that they are all scumbags? The MMA fighters that I have listed who do charitable work are just a few examples. Unless you are prepared to do the research, and prove they are all as bad as Randy Couture, then the broad blanket still applies and is the lazy way out.
There are actors, actresses, preachers, politicians, teachers, and on and on who more or less meet your description of Randy Couture but absolutely does not mean all of them meet that description.
This teacher is a proven scumbag, so all teachers must be scumbags. Really?