I watched the video of his live-stream and I can understand why Adam might have been pulled over because of the plates on his vehicle and the speeding thing.
I can also see how the second cop that pulled him over might have viewed Adam as being "difficult", as cops tend to like it more when people are fully complicit with their requests. They tend to be annoyed with people who know their rights and hold them to them.
Making it a long drawn out process, as he did by bringing in a sniffer dog I think is kind of his way of saying "I can be difficult too", but the actual arrest is pretty damn bizarre. Unless there's other information we haven't seen yet, it look like a case of authoritarianism at its worst.
Whenever I see stuff like this happen, the first thing I think is "I hope the pupper is ok!" Poor little guy. :'(