Spotters (and photters) are arguably worse still though. Afterall, at least bashers (usually) pay their fare, which on preserved railways, often goes towards the upkeep of locos / the railway in general, and obviously on Railtours, the fares mean more 'preserved' locos can be hired, and so on...
Therefore, bashers do contribute- it doesn't really matter what they say (and I can't imagine an EE basher ever criticising a 37 preservation project, however, it is likely they will criticise a 47 pres project- which is understandable, due to the 'rivalry' between Sulzer / EE)
On the other hand, people who vegetate on platforms or only phot, do not really help the upkeep of preserved locos- many photters do their fair share of complaining though- especially when it comes to 'flailing'. If they actually paid towards preservation of the loco they are photting, then they have a right to complain, but if not- they don't really.
I feel, overall, the 'bashers' do not have anything to be blamed for when it comes to lack of funds for preservation. IMO, it seems quite the opposite. If anything, 'bashers' are often given a bad reputation by a number of 'bad apples', who do avoid paying fares on tours/ galas, and flail / shout obsceneties. These make up a tiny % of the whole bashing community.