Ok, I see you are mightily confused with the issue.
Let's start with Fluoride.
1. It is possible to remove fluoride from water. There are 3 consumer available technologies to do it. You can use either:
1) Reverse Osmosis, or
2) Fluoride Removal cartridges (they typically use synthetic aluminum oxide)
In all 3 cases, it is nearly impossible, or VERY expensive to do it on a whole house basis so that your showers are also fluoride-free.
2. Fortunately, you don't have to remove fluoride in showers, it evaporates slower than water (unlike chlorine), and therefore the only thing you need to do in shower is not drink water to avoid fluoride intake. That is also another case AGAINST process #3 (distillation, long story, some distilleries are only concentrating fluoride).
3. Ionizing and oxygenating has nothing to do with Fluoride in water. The guys you've met probably want to up-sell you some very expensive products which are essentially not such a good water filters. By itself, ionizers are a very holistic and interesting subject, and obviously have ground as no serious scientist has a case against them (nor there's no explanation why they are so popular in Asia). Yet they are not related to fluoride removal in any way, shape or form.
If you need more, just email me, I guess I am not allowed to post any URLs here?...