The actual risk of "having the weapon taken away and used against you" is statistically insignificant. Seriously. Back when Kleck was first publishing his work on DGUs (Defensive Gun Uses) that was brought up a lot. The NIJ commissioned a couple studies which demonstrated pretty convincingly that defenders were disarmed in about 1/10000th of 1% of cases.
That's not an argument against training. And anyone who hasn't made The Decision should not own let alone carry a defensive deadly weapon. But it is an indication that you don't have to become an expert to effectively use these tools.
By the bye, the same studies showed that police were disarmed by criminals significantly more often. The studies hypothesized, and I concur, that's because of the very special nature of police work. An officer has to do much riskier things. He or she has to get close to, restrain and handcuff a suspect where a citizen is trying to make the attacker leave. In regular self defense cases the defender usually knows who the attacker is and why he's attacking. A cop arriving on the scene might not know anything except that there's been a report of a disturbance. Who's the attacker? Who's the victim? What do they want?