We have the same issue with our female Basenji. She is selective with dogs (which to play with and which to attack). Usually, she attacks dogs smaller than her. She will approach them nicely, in the beginning, they will start to sniff each other, then at some moment, she will try to grab the other dog by the neck in an attacking way. Usually, the other dogs sense this, and at the same moment, they have a back reaction. In can be fear, bark, or cry. She can act this way towards bigger dogs as well if they are under 1 year old. I think they try to smell and sense the energy/confidence level of the other dog.
Recently, I found a big dog park where you can walk your dog off leash. Thre are different trails and ponds. On weekends you can see over 200 dogs there, different sizes and ages. In this circumstances, ou Basenji got confused, maybe overwhelmed, she wasn't sure how to act in the beginning. But, because she needed to sniff with many dogs at the same time and be distracted by others around her, in addition, she needed to keep an eye on us so she doesn't lose us among other people, she didn't get in one fight. At the end, she stopped paying even attention to all the dogs around her.
I think Basenji dogs overall like to dominate the world around them. If they can put someone down, they will. I guess having them socialized with multiple dogs at a time, can make them more acceptable towards other dogs. Otherwise, you can use food treat distraction or any other distraction you can ( we can say" who is there?" and she will start looking around for squirrel, a rabbit, or a bird). If you put one dog in front of a Basenji most probably the Basenji one will consider the opportunity of taking over this dog.