1) He and his wife pled guilty to multiple fraud charges about 20 years ago now. Suarez had to serve 7 months in jail as part of it. I believe all the charges were technically misdemeanors.
2) He started out teaching at Front Sight and has continued a number of their shady practices
3) For a while he had his "Prison Knife Fighting" system training and associates knives and weapons.
4) He presented the pistol mounted optic on a Glock as though it was his idea.
5) He has espoused the "warrior mindset" "sheepdog mentality" and gone on a number of non-sensical rants on the internet.
I'm sure there is more I can't remember now - I think I recall something more recent about fraud/stolen goods.
Basically, Suarez has had controversy surrounding him his whole time as a trainer. When you compare him to someone like Clint Smith, Mas Ayoob, Craig Douglas - he would be a nightmare to have in court on your side.