I have generally avoided MSG since a kid and I have never cooked with it before but it is in a lot of things that we end up consuming anyway even if you are selective about what you eat.
Anyway, the dehydrated orange peel is part of what makes Malcom's rub taste great. At least IMHO. I have not tried the actual version with MSG in it but suspect that it would have more of that umami taste that is associates with MSG. The dehydrated orange peel has found a permanent home on my spice rack and I will be using it in a lot of future rubs. The MSG (Accent) is just on my shelf for some experimenting since I have not used it before. I plan to use it sparingly to displace some of the salt content. If you look at the ingredients on The BBQ Rub, MSG is one of the last ingredients listed (IIRC, ingredients are supposed to be listed in the order of their quantities). Salt, sugar, garlic and the orange peal are listed ahead of the MSG.
Another thing I read and I don't know if it is true or not is that orange (citrus?) can offset the effects that some feel when consuming MSG.
Though I am definitely in the camp of folks who avoid it when possible, I also am not convinced that it is as bad as some make it out to be.
https://www.fda.gov/Food/IngredientsPackagingLabeling/FoodAdditivesIngredients/ucm328728.htm