Way of Harmony
You have come across a lesson in learning to find the harmony of the universe, and finding the true way for yourself.
When your good intentions fail, as in trying to share what you have learned and you are not the instructor of a class, don't share what is not accepted freely. Practice your practice with each partner and move on.
As for overdoing a pin or a technique when an injury is present on your training partner, I would make sure that everyone in the dojo is reminded to tell their training partners of said injurys and not rely on taped or obvious supports for injured areas. Trying to train at full capacity with an injury is not only childish, but dangerous to both partners as pain can send some people into condition red ... an animal rage that knows no pain. (that is another story)
Whoever is in charge, whether it is by concensus or a black belt who supervises, sometimes if there is a conflict it must be brought into the open and settled.
The other thing about cranking down on your training partner .... sensitivity. Sensitivity is very difficult to master. Feeling the taughtness of your partners limbs, body, or their balance in not only awareness, but sensitivity. You might have to steel yourself to not say anything during practice, but work on your clearing of the mind during practice also.
The most difficult part about growing old is learning how to separate the emotions that cloud your thoughts to those that enhance your awareness. It takes practice, and sometimes it takes many years if you do not understand the difference between the two.
Step back. Take a new look at what has happened. See the situation not from emotional attachment, but with the clear mind that understands.
When words are not accepted, then crank the wise ass down and speak your peace calmly, succinctly. At this time, I usually give my little speach about how they can do whatever they want away from my presence, but in my presence I would have respect. Besides, it would be to their advantage to have me as an ally not a foe.
At least you wil have tried to smooth it over by all other means, before having a little talk when all else has failed. (this is only used when you can not walk away, and must maintain contact with the offensive individual.)