I wrote to Rocky Mountain PBS about this, last night, and have already received the following reply. At least they haven't ruled it out completely and thank goodness for WGBH in Boston:

Hello Kat,
Thank you for taking the time to share your valuable input with us. PBS national has decided not to feed the local PBS stations
Postcards from Buster: "Sugartime!" (Vermont). The rationale they have given us is that there are elements of this episode that parents should have the option of addressing with their young children at a time and manner of their own choosing. While PBS is dedicated to addressing controversial issues in the primetime schedule, they have decided that there are unique sensitivities in the area of children's programming.

WGBH will be making the feed available to those PBS stations who choose to air the program at a later date, most likely in March. Our programming director has not yet seen the program but is expecting a copy in the mail Monday. Upon viewing the episode, she and our general manager will make a decision about when/if to air the program. I will send you an email reminder if we have the program scheduled. I forwarded your email on to both our programming and communication directors. We certainly appreciate all the feedback we are getting from our viewers, both positive and negative.
Thank you for your interest in Rocky Mountain PBS,
Trisha Bentz Kendall
Viewer Services Coordinator