The main point being made by people about this statement is that the cycle infrastructure in this country is very poor. In a lot of places the cycle lanes have no priority at junctions, are poorly maintained and are not well connected with a lot of infrastructure. Given the choice, cyclists would often rather use the road, which gives them a right of way at junctions, clear road use rules (generally we all know how to use them) and we can make steady progress.
If you are not considered to be a road user then you have given some people the excuse that we should not have been there in the first place. That is a very vulnerable place to be and not something that the senior politician in charge of policy and transport infrastructure really should understand before making such inflammatory statements. Chris Boardman’s offer to take home for a bike ride would be an education, but highly unlikely that it will be taken up.