Your point is well taken - however you seem to miss another important ingredient, th elanded gentry that features quite prominently in the interesting piece that you posted.
The proverbial "rural idiocy" is not a natural state of the rural life, but a product of the feudal system and the plantation-like economy that depends on crude exploitation and reduces peasants to animals of burden. Such a system necessarily requires a strong landowning class that can extract the suprlus directly from peasantry (as Robert Brenner convincingly argued). This condition did not obtain in Sweden. Furthermore, it was the Swedish working class not peasantry that was the driving force for the socialization of the economy - but they did not have enough votes to pass the legislation in the parliament, an obstace that was eliminated after securing the alliance with the peasant party.
It should be noted that England had originally strong aristocracy that was able to extract the surplus directly (as Brenner argues)- however, its role was weakened through internal conflicts (e.g. war of the Roses), strong crown, and the development of commercial cities.
Free-holding peasants farmers are neither sufficient nor necessary condition for strong social welfare/socialist movement, as the case of US clearly illustrates. In fact, argument can be made that such free holders alone may form a core of reactionary movement (cf. Finland or the US).
However, your observation that strong urban bourgeoise inhibits socialism needs to be qualified - it may inhibit more radical versions (such as nationalization of social protection) but often leads to strong welfare states (cf. Germany or the Netherlands), usually in collaboration with conservative elements (especially organized religion) that are partners in such welfare schemes - often as the means of appeasement and pre-emption of a labor movement.
Wojtek