I agree with a lot of what's been said so far.
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I think part of the problem is that, whether they be young or old, newcomers to the trans-community don't understand how these terms have been used in the past, nor do they understand what that past usage means to the members of the trans-community at large. Kind of like if a sheltered white farm kid moved to the inner-city, and started to use the word "Nigga" with their new black friends. In either case, people tend to react out of offense first...sometimes violently (whether verbally or physically)...often failing to explain where their feelings of offense and hostility come from. Sometimes, when rejected from the initial group, a person might think their derogatory usage of the term justified, instead of examining their word choice further.
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Sometimes younger transitioners...being so different from their cis-peers....in their quest to see themselves as real...legitimate...genuine...(I think we've probably all felt a lack of those things at some time or other) latch onto such terms, not realizing (and with some...not caring) what the further implications for others might be (ie. 'I'm real/genuine' being most important to them...with the unthought/unspoken 'but you're not' often not even realized)...especially since often, at first, they have no real contact with those who would be effected by those implications (ie. older trans people). They use the terms, because they think those are the terms they're supposed to use. (not being completely informed)
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Ignorance is understandable, and should be expected in anything at first.
To feel offended by ignorant words is also understandable.
Unfortunately, neither position is particularly helpful in resolving these issues of division and hostility.
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Just like with "nigga", when a community continues to use a derogatory/divisive term (even if that term is intended in a friendly way), it can be very confusing for newcomers. Unfortunately, the trans community has not completely stopped using these "primary" and "secondary" labels. They're old...archaic...out-moded....but will probably have to be explained and re-explained to newcomers for many years to come until they die out completely.
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The easist thing to do when offended is to lash out right back at the offender. With many...young or old...going through a 'second puberty' of sorts, it can be difficult to keep ones wits about them and respond with a cool head. Often in finding ourselves, emotions run high in the forefront, and we can easily forget that we, like they, make mistakes too...and are in need of a little extra understanding at times.
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It's just like the homosexual community. We don't have two terms for homosexuals....one for those who are brought up in accepting/more-tolerant environments and feel safe enough to be themselves from an early age....and one for those who don't. We only have the one term. When they come 'out of the closet'....they're gay/lesbian....not 'secondary-gay/lesbian.' The terms 'primary' and 'secondary' in the trans community come from older times and philosophies best left in the past.
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The maturity to let cooler heads prevail, so that an understanding can be reached is what is truly needed, but can be difficult to achieve at times.