Currently it's not possible to use the poison tool to apply poison to gloves. Coming from I monk, it would be great if that was made possible.
Poison in most cases needs to enter someones body via blood or digestion. While there are contact poisons, they are the exception to the rule. Punching rattlesnake venom into someones head by smearing it on a boxing glove doesn't seem like the ideal way to do it.
There are also glove items that are actually bladed gauntlets which would certainly be acceptable, since those are not actually hands you are striking with, but sharp punching weapons. It would be impossible to script a way to determine if the specific gloves are appropriate or not however, and nwn will still think that they are a bludgeoning weapon even if they do have like 1d6 piercing on them and not applicable to poison in the first place. Maybe if the glove had a additional damage type: pericing or slashing.
Per default poison weapon only works on slashing or piercing weapons. Not on any bludgeoning. Gloves are in the bludgeoning category.