It really depends on how you can cope with him. If you can deal with the episodes and convince him to calm down, there is no need for medications.
Some medications have side effects and may not stop his delusions and wrongful logic anyway. Seeing a psychiatrist won't help - the GP/family doctor can give him the antipsychotic drugs as well. My FIL never really saw any psychiatrist at all.
My FIL had been in his old house with Alzheimer's for at least 4-5 years before he was moved to the residential house last year. During the whole time, we had personal caregivers and we stayed with him when we visited him a few times a year. He had never had any antipsychotic drug. What we had done was to cope with his fantasy and deal with it. He wanted a wife so we played along (not to make it real) and he wanted to work, so the caregiver pretended to listen to his "talk". When he was upset, they walked him to the lake or drove him to the lake and etc. It is a lot of work though. Thinking back, toward the end he might need some antipsychotic drug as he was going crazy in the hospital. He pulled out all the ivs and tubes...
You are right in a way, however, there is always a limit. So be flexible about it.
Also you should not remind him that he has dementia - most of them don't want to know and would be very anxious about it. My FIL knows something is wrong with his brain (he would make a circle around his head) but he denies that he has Alzheimer's. He probably knew that later on but he does not understand it anymore. (He is in stage 6/7, near the last stage.)
What you should really do is to distract him - don't bother to tell him oh it is his dementia that causes such delusions.... It would upset him more.
The caregivers for my FIL turned off the TV on bad news and changed the channel or took my FIL out for a walk to distract him from his delusions about the bad news.
Also my FIL never sees invisible people - he treats all people around him as his colleagues or potential girlfriends... The reality is his fantasy.