The concept of mandatory bars and disbarring seems, ironically, to be unamerican. I can see having bar membership as an optional accreditation. We have ASE certified mechanic, or CCNA IT guys. Actually disallowing someone from doing a job, though, merely because someone else says they're unqualified seems incongruent with basic capitalism and free market principles.
Only if you distill the reason down to a very simplistic level. Remember that professional organizations are made up of peers. Yes there are politics involved; politics are always involved with groups. However, if someone's peers says that they are unqualified, that should carry some weight. In the case of Thompson, he wasn't merely disbarred because of his qualifications. He was disbarred for abusing the legal process for petty, vindictive, harassing, and arguably insane actions.
Unlike other professions lawyers have to oppose each other. It's part of the job. Thompson seemed to take it personally every time a lawyer opposed him in any way by doing their jobs. He took it personally every time a judge ruled against him in any way. To him everyone was on a crusade to get him.
For example, in the Devin Moore (Strickland) case he was thrown off the case because he seemingly lied in his pro hac vice application. The question in the application asked whether Thompson has ever been in a disbarment or disciplinary proceeding. Thompson's reply was "None but please see attached letter." His letter only mentioned a complaint made against him. In fact, Thompson had been in a disciplinary proceeding and took a guilty plea. The judge found Thompson's explanation of this major discrepancy unpersuasive and revoked his license throwing him off the case. For 18 months after that, the judge received documents and complaints 3-5 times a day almost daily (even after the case had been resolved in the court). He also accused the judge of "fixing" cases and witness tampering. In the same case, he sent a letter to the opposing lawyer who was female: "You disgrace us as lawyers. Shame on you. Shame on you as a woman as well."
In another example, Thompson accused Al Cardenas of Tew Cardenas: "More specifically, Mr. Cardenas personally and his firm collectively have protected the distribution of pornographic material to children and helped target me and my family. . ." Al Cardenas had no prior relationship or dealing with Thompson. His only connection to Thompson was that his law firm shared a client with another lawyer who sued Thompson for defamation. The convoluted saga was that Thompson had sent complaints to Beasley Broadcasting Corp, LLC about their radio programming. Beasley retained Norm Kent to address complaints by Thompson. In the course of his dealings with Thompson, Kent filed a suit for defamation and won $50,000. Beasley had the law firm of Tew Cardenas on retainer for other legal matters. Al Cardenas was a managing partner of Tew Cardenas but never interacted with Beasley. That was his only connection to Thompson.