I'm curious if the anti-parser crowd would have a problem with a parser being implemented in a limited capacity such as having it available for:

1) Training Dummies (what the hell good is a training dummy unless you have real time feedback. Yes you can practice your rotation on it ad nauseam but that doesn't really benefit you if your rotation does poor DPS to begin with)
2) Extreme Primals (Story mode/Hard mode primals would not have a parser option as it is completely unnecessary)
3) Savage tier content (This is where most of the pro-parser crowd exists - you have fights that have constant DPS checks and no way of determining why a group is not meeting said DPS check unless someone is running a parser. As a PS4 player, I can only hope that it's not me who is holding everyone else back but I have no real information on if it is or not until someone on computer tells me as such.)

Beyond those situations, the use of a parser will absolutely be used to detrimental effects. Parties/party members do not need to know their DPS in dungeons/24 mans/Alex NM/Story mode battles/Any open world content other than the training dummies as none of these situations truly require a very tightly tuned DPS check. However, within the top-tier content, parsing data can be a holy grail of information for raid teams and even PUG groups trying to participate in this content.

Will it be used to exclude people from the higher endgame battles? Yes, undoubtedly, but if Player A isn't able to meet their portion of the DPS check, I'm sorry but they have no place in a party attempting a fight that has such tight DPS checks until they are able to improve themselves. Furthermore, it would be much easier for them to improve themselves and be able to participate if they had a metric which they could measure themselves while practicing their rotation.

However, by limiting the content a parser is available in to these types of fights, the casual crowd, who typically do not even attempt to undertake these kinds of fights, would remain free of having jackasses constantly berate them because they may not be doing the best DPS humanly possible in Antitower Roulette.