This bit comes from near the start of the episode when it looks as though Travis might manage to destroy the Liberator. Avon and Blake are very close here - they're either arguing about Blake's plan or about to kiss.
I think it's both.
Avon spends a lot of the episode watching the Blake/Travis duel. He is clearly worried about Blake when it looks as though he might lose. This is a bit like Mr Spock watching Captain Kirk fighting the Gorn captain in Arena.
"I have never understood why it should be necessary to become irrational in order to prove that you care. Or, indeed, why it should be necessary to prove it at all."
The duel finishes with Blake and Travis fighting with sticks, one-on-one, manny-a-manny.
Avon is happier when it looks like Blake will win.
Blake does win, of course, and - like Captain Kirk does with the Gorn - he spares Travis instead of killing him.
Travis goes back to his ship to try again next episode.