It's not enough to just aerosolize the LNG, it needs to mix with air in a rather narrow fuel-air ratio of 5-15% to burn. Further the flame front speed of methane in open air is only 4 mph - it won't explode, though as the flame front spreads it might kind of look like an explosion (think about what it looks like when you light a gas stove or grill). Such a fireball can potentially ignite things in close proximity, but there won't be a pressure wave that damages structures, so you can't have a situation where one tank 'exploding' causes other tanks to explode, though in a crash it's easily possible multiple tanks are damaged.

Natural gas is an explosion hazard in enclosed spaces. If you walk into your house and smell gas, that's very dangerous. Note also that even if there is no explosion hazard, fire is still dangerous.

If you are uncomfortable with rail transport of crude, that's a perfectly legitimate stance to take. Honestly, transporting any flammable substance (and many non-flammable ones as well) does pose risks. If you know the risks and benefits and think the former outweigh the latter, let people and especially your representatives in government know. However, society generally seems to accept rail transport of oil and similar chemicals, so outrage over the transport of a less dangerous substance seems like it would be more likely to come from a place of ignorance than rational analysis.