Most users you're trying to message have their account disabled for newbies to message them, and i don't see the need for you to be doin this for nothing, you can get a temporary ban once the moderators keep receiving a consistent report on your PMs, instead of you sending PMs, try create a thread and discuss anything there, if its about privacy, check the users profile if they have their website or telegram username on it and communicate them through such means, lastly, you may wait till you rank up to Jr member or full member rank before you can be able to send PMs, still with that, some can choose to block you from sending them PM.