I really do see what you're saying, in theory.
My problem is this: as a voter who they are trying to persuade to vote for them, I have to look at what they present now that they are given the opportunity to explain it to me in their own terms. If UKIP knowingly chooses a candidate who a) holds some rather objectionable views that are utterly contrary to the party line and b) isn't particularly loyal to UKIP at all, what am I to learn from that? It's not exactly extolling their finest virtues is it, if that's the best they can offer. I can't vote for them based on their ideals. I have to vote based on the person who will be representing me and voting on these kinds of key issues in Parliament - and this guy will not be apparently towing the party line so what agenda is he following exactly? Who knows!
And both his reputation and UKIPs is being utterly trashed now. Their European agenda is utterly vanished beneath a homophobia row. And they picked him!
It makes their complaining about adoption issues sound hollow when their own man is denouncing the rights of others to adopt under a nice big picture of their logo.