This is probably :late: but someone in this page brought it up so here's my take on the situation:
A lot of people are confused and angry that Dobson clearly thinks that letting Nazis speak will turn more people into a Nazi, but this isn't as uncommon as you might think. Dobson just, in classic Dobson form, managed to take a retarded idea and spin it in an even stupider way. Dobson, like all ideologues, doesn't think there are people with bad opinions, there are only bad people. He can't comprehend the idea that someone might disagree with him now, but have agreed with him in the past. Or that someone who disagrees with him could be convinced to agree with him in the future. He doesn't know what it's like to be, in any way, different than Andrew Dobson.
Dobson recoils with disgust at the idea of genocide, and yet genocides have happened in history, and there are occasionally people who will unironically advocate genocide. For a normal person, there's nothing confusing about it. Some people are stupid, haven't had the same upbringing as you, and have taken their ideology to extremes. For someone like Dobson, it is completely incomprehensible. Nazis might as well be Lovecraftian monsters for all the sense they make to Dobson.
Searching for an easy answer, Dobson simply assumed that certain people weren't born with an instinct that tells them right from wrong. He can't justify his opinions, he simply feels emotional about certain things. His instinct when he hears someone disagreeing with him is to ree as loudly as possible, so anyone who wants to actually debate Nazis must not disagree with Nazis. And therefore the only way to stop the Nazis from gaining ground is to stop people from debating them.
I'll bet any amount of money that Dobson doesn't actually know why genocide is wrong. He's just watched enough TV saying genocide is wrong to have internalised it. If you manage to trick him into trying to justify his opinion, he'll probably just say murder is bad and not try to find the fundamental logic behind it. If you're lucky, he'll spout something about oppression culture. He doesn't think it's ok to debate Nazis because he will lose any debate that doesn't involve yelling angrily and tracing shitty comics, and Nazis don't get convinced by yelling angrily and tracing shitty comics.
Dobson, like all ideologues, thinks that his side is inherently right, there's no logic behind why they're righ. He thinks that if someone isn't born with an instinctive hatred for genocide, the only possible way to convince them that genocide is wrong is to beat it into them at every opportunity. He thinks that education is simply repeating the correct answer until your pupil has memorised it. Possibly a result of his schooling being terrible, definitely a result of him being an idiot that can't comprehend other people.
Ironically, Dobson is the one lacking basic brain chemistry. The only way to explain this level of retardation is a complete lack of empathy. Not the informal definition of empathy which means you try to make people feel better or something, but the actual definition, the "ability to understand and share the feelings of another". Dobson can't understand other people in any way, so he creates an insane narrative that lets him think of them as fundamentally evil.