Thank you Craig for your careful observation and for your explanation and analysis. There are many performers who classified themselves as "Magician and Mentalist" so for that reason, do you think there are any performers out there who can convince their audience to belief in mentalism even though there are also a mix of magic effects in their act? When my friends saw Derren Brown performed on tv, they ask me if I know how he did his "tricks". Even though he is a mentalist, it would still be very difficult to convince his audience what he did was real, and the same applies to magic. Just my thoughts.
Understand, there are people that believe Copperfield really flies too. . . one lady I knew claimed it was David's use of the Kabala, give that David is Jewish by birth.
While presentation is everything you have to look at context and how MOST that mix magic with mentalism hurt the the latter. Brown, while I'm not overly thrilled by him, is a decent showman and a hint charismatic. He presents much of the mentalism he does as psychologically based "experiments" and because of this, he can get away with the mixing or "blending" as it were. Your claim does have a lot more to do with things and if you're a cynic, such as Brown tends to be, then meshing Magic with Mentalism is status quo . . . the agenda is to neuter Mentalism and those Mentalists that proudly call themselves Psychic Entertainers and not just Mind Readers (though many of them do the work "for real" as well).
The argument about people like Brown, Banachek and even Osterlind doing magic & mentalism is old. . . even Dunninger did big illusions in some of his shows. the common factor with all of them is what I've already stated; they are all skeptics and while they will seek to do the best possible demonstration they can, they are still looking at what they do as a trick and that in itself creates harm to the art. I probably should point out that Larry Becker & Lee Earle both admit that they do Mental Magic more than pure Mentalism because of how they blend the two skill sets and how Larry in particular, does almost everything with a deck of cards (a big Taboo for most Mentalists, believe it or not).
Fact is, to be successful commercially you must include a bit of Mental Magic because it adds production value and helps lend to the public, an "out" -- they see something that looks more like a trick or something that's "familiar" and it helps them to relax. Another odd fact is that I have personally developed big illusions that were specifically designed to work in a Mentalism program. . . if you were to have access to the now dead On-Line Visions eZine (one of the oldest and largest publications for years) you would find articles where I discuss this and how such steps help the Mental performer explain other principles allied with Metaphysical thinking such as Astral Projection, seeing the Aura and so forth. The thing is, we have framed such pieces by way of the presentation; the Aura routine is more of a "what if we could" type bit while the Astral Projection routine would remind you more of a Spirit Cabinet act, even though it goes a bit beyond that and avoids some of the usual gags.
Since the inception of Mentalism there has been an obvious relationship with Magic but they are not the same thing and in order to gain the strongest possible advantage, separation from magic is always best, this has been proven historically more than a few hundred times vs. the handful of successful acts that run contrary to this claim. The biggest thing that "justifies" this mix in recent years, has been the TV exposure to people like Brown, Angel and even Blaine rather than people actually learning the art from the working pros; Commercialism always fixes itself into the consumer mind-set, it's that simple.
HOWEVER. . . there is an underground movement known generally as Urban-Shamanism that you can read threads about here and at E both. This genre does successfully blend the two art forms along with puppets and storytelling but it's done as if the magic were real. . . just as real as the mentalism and then some. The effects are carefully chosen so as to meet certain very specific criteria and the performer's attitude and actions are 99% of the whole ordeal -- they are literally their persona 24/7. . . a Shaman in modern environs -- a "holy man" if you would.