This is a video interview with Geshe Kelsang Gyatso (filmed at least 10 years ago) about how Buddhists view other religions. In particular, Geshe Kelsang is asked how Buddhists view Christianity. He said that it is a very beautiful religion that shares a lot of similarities with Buddhism. Some people love both religions, but in the end they should choose just one. Otherwise there is fighting inside.
This is similar to why, in the NKT, many practitioners say it’s best to focus on one tradition. Because, if we follow multiple traditions, we will be confused and have an internal conflict about which path is correct or which teacher is correct. This is why most practitioners in the NKT focus on one tradition. Not out of sectarianism or coming from a critical attitude toward other traditions.