I'll answer to try and get this back on track. Whether I'm a liberal or not is for others to decide I guess.
The conservative position on things like pornography, gay marriage, drugs and online gambling is generally to prohibit or overbearingly restrict them. Liberals tend to be more permissive on these issues while wanting to ban or restrict firearms, smoking, dodgeball and the accumulation of wealth.
Well, don't get me started on dodgeball!
I'm not sure what "permissive" means exactly in this context. I'd say that pornography and online gambling should have some restrictions for sure. In both cases we do need to be concerned, as a society, about children having access to either one and the potential damage that can come from that. Also, there are addiction issues associated with each.
On your second set of issues I'd argue that smoking is a health hazard to second hand smokers (I lived with two smokers for eighteen years and smoked for a while myself). I do support firearm testing as they do in Europe. So your question is why?
I'm not going to get into economics in this response.
From my point of view, we have to act as a responsible society and place the good of the overall society above the good of the individual. In that sense, I disagree strongly with the Thatcherite sentiment that "there is no such thing as society, but a collection of individuals..." That does not mean that society gets to run roughshod over anyone, as human dignity and human life must always be preserved. That is why I cannot support abortion, capital punishment, euthenasia, unjust war, racism, and other such violations of life or dignity.