You can see the House discussion below. As FABB points out, the legislators frequently don't know the law (like when cyclists can ride two abreast or where cyclists need to ride).They also act like the 2-foot law was passed "a long time ago." At the end some gentleman points out that actually that was passed in 2004.
One of the complaints is that it can't be enforced - but there's currently a 2-foot law; how is that enforced?
Another concern is that it makes it impossible for drivers to pass without moving into the other lane - or to pass at all. Which seems to be placing the ability of drivers to move unimpeded above the safety of all road users.
The question of "how is one to know what is three-feet?" comes up. But the point is that drivers underjudge the distance and that by asking them to aim for 3 feet means they will less often mistakenly give -0.01 feet (which is the concern).
One legislator says that he saw some cyclists break the law once, so he doesn't want to pass anymore laws for cyclists. Not until cyclists follow the law. I'll be you dollars for doughnuts, he doesn't have the same opinion about gun owners, drivers or pedestrians.
Another legislator asks "what is the downside of passing this law?" and none of the others really have an answer. One person does make a nonsensical case. On the one hand, he claims, the law won't change anything and thus won't improve safety, on the other it will do more to impede traffic. With all due respect, it can't be both. Either some drivers will give greater passing distance or they won't. If some do that will improve safety. It might also impede traffic. But there is no way that it won't increase passing distance but still more greatly impede traffic.
This is followed by one legislator who would like to retain the right to unsafely pass cyclists who are illegally riding two or more abreast.