I actually wrote most of the machine learning content at Dataquest (where I work) and I started with k-nearest neighbors because it's way more approachable (https://www.dataquest.io/course/machine-learning-fundamental...). Little math, very visual, easy to program, etc. I used this easier-to-approach algorithm to teach the key other ideas in ML (test/train, cross validation, error metrics, etc).
Happy to chat more about different pedagogical approaches to teach machine learning!