I work in a technical role and I'm frequently put together with all the other folks with a similar job title in my office. I have a coworker, let's call him Brandon, who has really poor professional judgment, but because he sounds really convincing, and has what seems to be legitimate credentials, most people take him seriously on surface level. However, in any task where he has to do anything at all, he's shown a really poor understanding of the task, and what's worse, he has a communication style of sounding 100% confident. In my team, we're seen as the SMEs for over 100+ clients, and I'm starting to get really concerned that some of my managers are redirecting folks to him. He has already given people wrong information several times, and it's been on me to correct him - even though I'm not his manager. Another issue is that there really aren't any technically skilled managers at all, so other people can't see through him.
The final issue, and this is somewhat personal, is that he has said something that struck me as really inappropriate on an HR level. He has also mentioned doing things that would have violated department protocol, and when I asked him about it, he backtracked and said he was joking. I don't want to be someone who trash talks my colleagues, but as my team starts to try to make us have a more public role as SMEs, I am really concerned about him publicly interfacing with anyone at all, both because he gives out wrong information, but also because of the other more interpersonal issues.
During my time here, my own manager left and I was put under Brandon's manager. I'm deathly hesitant to mention any of this to my manager, because I know my manager is the one who chose Brandon and likely closer to Brandon than to me. (There is also this other thing happening where Brandon is a white male and I am not, and I am thinking that some of our clients prefer going to Brandon for this reason even when it's known I'm unofficially the senior lead.) There are more senior folks here whose professional judgment I trust who I could share this with, and have them understand to stop routing folks to Brandon, but again, I wouldn't even know how to put this.
Since I am de facto the one in charge of making materials for our clients, it's possible for me to simply exclude him from the process without saying anything, but my manager really pushes for me to include Brandon in literally everything. I don't know how to tell my manager "no" in these situations. I could state that Brandon is not at my level of technical expertise and that's the reason. I should add that everyone agrees I'm the leader in this field already, and it's evident to everyone that my job requires much more technical expertise than his, partly because I was hired at a mid-career level and he was at an entry level, even though our actual titles are similar. However, I'm afraid that makes me look really snobby.
Any advice would be much appreciated.