“Rot op met deze &*%$#@! fiets” roughly translates to “Fuck off with this fucking bike” .
In other words somebody is displeased with Doede’s choice of bicycle. Below, the same in better detail.
Here we can read the smaller text below.
Dit is een asociale fiets hij is echt te groot en waarschijnlijk kan ook jij er niet normaal mee fietsen
And in English: “This is an antisocial bike it is really too big and you probably also can’t cycle normally”
Now let’s consider this more carefully.
Now if anything is antisocial it’s telling people, unsolicited, by sticking things on their bikes, that they have too many kids, that they ride a bike that’s “too big”, and that they probably can’t ride a bike normally. So fuck off, you righteous asshole! Put stickers on your own bike and don’t tell people how they should live. Be happy that Doede rides a bakfiets (no wider than the handlebars of a normal bike in case it matters) instead of driving a Cadillac Escalade. And be happy that you live in Amsterdam, cycling capital of the world.