It's just dumb. Some random media-horny guys from an online platform called GeenPeil thought it a good idea to force our government to waste millions of euros on a national referendum on the trade agreement with Ukraine. They got the required number of signatures to make it happen using social media, and now we have a referendum. The 'against' lobby is trying to make believe that the trade agreement is a step towards EU membership for the Ukraine, which is just not true.
They're just trying to make it look like voting no here is like voting against the EU, and they are handily playing that sentiment.
Sadly, most people who are going to vote haven't even read the trade agreement (which is understandable, since it's hard to read, dull legal stuff mostly about import and export taxes and calibrating tax and banking rules in an effort to make it easier to combat corruption).
I'm not a big fan of referenda, especially when they are about rather insignificant subjects that have no direct impact on your average voter, like the trade agreement with Ukraine. Which by the way, is very similar to trade agreements we already have with Morocco, Japan, Pakistan, and a couple dozen more countries, but about those you won't hear anyone screaming that those deals will lead to EU membership.
Putin for one will be sniggering when a Dutch majority votes no. The trade agreement we are voting about now is the same one that started the whole Maidan protest and the subsequent annexation of the Crimea. The former president of Ukraine decided not to sign the trade agreement, after which the Ukrainian people took to the streets and the president fled to Moscow.