Proponents of a delay include people like Donald Tusk and Angela Merkel, so not exactly people who'd be considered to sympathize with people like Le Pen.Only reason to get the delay is to postpone brexit after the european election so their friends (Le Pen, Salvini, and the other wannabe dictators) can avoid the immediate backlash once people understand what it means to have a °no deal° and exiting the union. Elections in EU are coming very soon. Probably that's why.
As long as Brexit happens by the end of June, there's not really a problem with an extension. The EU is not interested in a hard Brexit nor do they want the British press or politicians to somehow be able to put the blame on the EU ("We'd have figured a deal out if they just gave us more time!").
It's only if Brexit gets delayed past June that severe problems would arise due to the upcoming elections (which Britain would need to take part in). Would be still possible, but there would be strings attached (like a GE or another referendum).