It takes me a while to sometimes read everything and sometimes longer to figure out that I missed something.
In an earlier post, on a slightly different thread, the question was raised how to deal with "roguish" practicioners" (there I managed to squeeze in both the British and American spellings).
Since "roguish" can mean mean and ill tempered, or, it can refer to persons not affilitated with normal human society, the question is somewhat unclear. Never mind, I'll answer both and possibly a third when it occurs to me.
Sometimes you will have people from another style come into your dojo to "check you out". Occasionally they have the manners and courtesy of a pug with gas. Such persons may actually seek your permission to train in your dojo then proceed to "trash" your students or otherwise set out to prove that their aikido is "better" than yours. For those who are hurting your students, politely ask them to leave. If their sensei has bred any respect in them they will. If they become belligerent and combative, repeat your request and add that as a private business that if they do not leave then your only recourse is to call the police. Do not give them three requests, simply act.
If you have this type of experience with such bad elements, presumably you know who their sensei is, as such boors usually trumpet it about. Make certain you know their name, then on another day call their sensei and let them know what happened. Do so calmly. Their sensei's response will probably tell you where they learned their behavior. Fortunately such occurences are rare.
Usually, the "roguish" person may simply not understand what your rules are and is following what they think is right. A simple "We do it differently here" should be enough to clue them in.
Then there is the visitor who comes from another organization who is focused on being "right". There is an US organization which is noted for turning out many such teachers. All they ever hear is theirs is the right way and everyone else is not. As a consequence, I am able to discern their organization by how often they say "You are not doing that right". (No I am not going to mention this organization by name, that would not be right.)
When confronted with this type of person, the phrases "We do it differently here" or "We are exploring an different principle in this art" both allow you to inform the person that your expectation is they are there to train in how you do things.
Your confidence in your own training and your depth of understanding of the principles and reasons behind your training is your best proof against the "boors, rogues and other not-so-nice people".
I hope this helps to clarify, not muddy, the waters.
Yours In Aiki,