I have a similar problem round here,I try to avoid other dogwalkers if possible.My dogs are quite good,and recall well,but will snap if rushed at by strange dogs,one of mine was minding her own business,in fact we were doing a bit of training off lead,at the time,when I heard this manic yapping getting closer.A terrier rushed at her and she calmly pinned it down! I said"Jess!get off him!"she let go,the little dog got up,shook,coughed,and ran back to his owner,a sadder and wiser little dog.I think the reason why a lot of people who let their dogs rush up to others,and refuse to recall them,is simply because they cant!