Under what conditions is it proper for Buddhists of one tradition to try and proselytize Buddhists from another tradition? Under what conditions is it improper? What harm can be done? What fruits can be gained?
Can cross-tradition debate be a good thing? Is it ever a bad thing? What is the proper motivation to do so? What are improper motivations? What is skillful? What is unskillful?
Is it desirable to grant a modicum of respect for all traditions? How should this respect be manifested? What are examples of disrespectful dialogue and how can/should the line be drawn?
Note: I'd prefer if these questions are not used to proselytize or engage in debate about Buddhist doctrine... but rather to answer the questions above.
... and references to dharma teachings, historical events, or opinions/literature of noted teachers also welcome and encouraged!