I know what you mean... but at the same time, I thought Solomon made a pretty clear choice earlier on...?

...and not just when he'd massacred the Silurians, in "cold blood", so to speak... I mean there was definitely at least one or two points The Doctor offered him a way out, I thought?

The bottom line... Solomon was probably every bit as ruthless and twisted as a Dalek. The Doctor has despatched those much quicker...

...and don't forget he blew the two robots up as well... they came across as fairly sentient entities... and not too in control of their own fates, being slaves to Solomon. Or is that going too far into Asimov territory for the DW universe?