As most things are in life, it isn't exactly a simple issue. The author of the linked essay is an expert on ivory, probably the best in the country. He only buys aged preban ivory, and has been helpful to authorities in the capture of those involved in the illegal trade. From one perspective, supporting him is supporting the crackdown of illegal ivory, therefore supporting the fight against poaching.
I have read/seen articles talking about the guards of reservations having trouble affording bullets to fight off criminals who would want to break in and steal the ivory they have stockpiled that they can't sell. They can't afford the high cost of health treatment to the herd that they were once able to due to sales of ivory after the weak members of the herd died or were culled.
Who knows how much of it all is propaganda. The simple fact is that elephant ivory, if properly managed, is a renewable resource. If left alone, due to civilization encroachment, lost of habitat, and poaching, herds left to fend for themselves are less healthy than managed herds. It is true if there suddenly was absolutely zero demand for ivory around the world, poaching would stop. That isn't going to happen. If obtained legally from a reliable source and the sale and distribution of cues is followed within the legal limits of the law, it should boil down to personal preference and personal conscience whether one wants to use a 30 year old piece of ivory in a cue that otherwise would just sit on a shelf or be burned.
Kelly