Speaking of "Heart Of Glory"
When one of the two Klingons picks up a child in the Enterprise's corridors, Lt. Yar quickly calls in a hostage situation. If Worf's chubby Human brother had picked up the child would Yar have done the same?
Being allies doesn't mean you trust each other.
The Enterprise crew as a whole tend to treat the situation as a possible threat. Not so much in the sense of 'These are our enemies', more like they still
hadn't quite got to grips with the peace that must have ensued for decades. I think Timo
is probably right in saying that even with an alliance, the Klingons and Federation more or less just stay out of each others way. They aren't enemies, but they aren't exactly friends