Yes, there shouldn't be anything wrong with being a radical ...
I would agree wholeheartedly, Rhi. Interestingly, last year's reactionary can become this year's radical simply because of changes in social attitudes.
I'm no linguistic purist - fingers and brain rarely work in harmony for starters - but words should at least be used with accurate meaning.
But what counts as 'accurate meaning'? For instance, as we've seen on the 'Lord's Prayer' thread, the word 'tempt' has a different meaning today to what it had in King James VI time. On a shorter time scale - we have words like 'wicked' and 'gay' that have changed meanings dramatically in the space of 20+years and 60+ years respectively.
Even 'radical' could be seen to be synonymous with 'zealot' if you look at oxforddictionaries.com. The third section under synonyms of 'radical', is "a radical political movement" and you get words such as
extreme, extremist, fanatical, militant, diehard ...
If you then look for synonyms of zealot, you get this selection:
fanatic, enthusiast, extremist, radical, Young Turk, diehard, activist, militant ...