After taking off, I contacted the departure freq on the approach chart for
0W3. The controller chewed me out for departing VFR, made a comment that it
was unsafe, and sent me to another frequency. I tried the new freq, and
this controller chewed me out even further, refused to get my clearance, and
told me I should have gotten it on the ground.

That's very odd indeed. Popups are one thing, but a filed flight plan
should have gotten you a better treatment. In fact, picking up the
clearance airborne (assumming you can maintain VFR, of course) is
usually doing the whole system a favor, as opposed to being cleared by
FSS with void time and blocking a relatively large chunk of airspace
for 10-15 minutes.

My guess is you simply ran into some a**holes that day, VFR is VFR, I
believe you are not creating any operational problem by asking for
your clearance that's on file. Or maybe the controllers believed you
were IMC because of some erroneous bases report they got earlier. If
the specific time/location is inconvenient for ATC, they can always
ask you to standby or maintain VFR to some fix/altitude. The scenario
where climbing will put you in the clouds bellow their MVAs can be
handled by declaring you can maintain own terrain separation up to
blah (but make sure you really can).