Considering the fact that the British only contemplated using gas against military forces of a genocidal state invading their country, while Germany murdered millions of Allied citizens by gas, saying that "Churchill was prepared to cross lines that Hitler wasn't" is a dishonesty to say the least.
The same with Luftwaffe-it engaged in terror bombing of Allied cities and civilian population from the start of the war. British didn't start it.
Perhaps. Although Hitler always nixed the military use of gas - and, without wishing to get bogged down in conspiracy theories, there's no evidence that he personally sanctioned the use of gas on camp inmates.
You can emotionalise this argument as much as you like, but the facts are that Hitler never once ordered or sanctioned the potential use of gas against troops in the field (probably because he was gassed in WWI), but Churchill did, explicitly issuing orders for contingencies to use gas in the event of Sea Lion).
Now, does this make Churchill worse than Hitler? Of course not. Does it make this argument anything more than a petty, pedantic squabble over the semantics of a superficial moral scale? No. What it does mean, though, is that it's not 'dishonesty' to point out that on a factual basis, Churchill did some things that Hitler did not. Hitler did things, however, that were a hell of a lot worse.
And we're not talking about Allied bombing targets, only British ones. The point made was that the Germans didn't bomb British terror targets until the RAF struck Berlin in early 1940 IIRC. Whether the Germans bombed Poland earlier than that is, while tragic, irrelevant to the matter at hand.