Though I'd like to see them on the fringes, political radicals would be wise to try to allign with more centrist groups. Because, by and in large, the center is where most people in the world stand politically. So yes, they should make friends with the centrists as often as possible if they want sway.
While they probably would not be considered radicals anymore, if they the did that. What do radicals actually get besides not taken serious and making the country worse? Sure, they probably profit in the short run, if they are really good at spreading propaganda. Getting many people to buy into this falsehood. The problem is when people find out most everything is all made up, people tend not to be to happy. Outcomes usually work out much better when people give a little, while taking a little.
No one likes to side with radicals on the extreme of the political spectrum. In order to get things done in the government, everyone needs to compromise sometimes. In a free society, there needs to be leeway for compromises and concessions. Democracy is not easy, and we al need to live together in one country.
They should rather, associate with centrists to find common ground and goals in order to make the peace and build a better, more peaceful future. Radicalism, with its emphasis on absolute solutions, pure good and evil, splits people apart and leads to war and all the losses that go with war. It is only in forgiveness and tolerance that mankind advances the cause of freedom overall.
While it may seem like a good idea for political radicals to ally with more centrist people so they can achieve their goals piecemeal it does not mean that they should do so or that they are willing. Political radicals are rarely interested in compromise and attaining their goals slowly, is something they rarely consider.