+1, but in many years of hauling bikes quite a few of which were made before lawyer lips were used, and some with them filed off, I have never had a problem with a fork coming loose from the rack.
Last year TWO of my friends' bikes with filed-off lawyer tabs unclipped from roof racks. One was on a car I was riding in, and I know it was racked carefully (though I didn't do it myself). Luckily someone in another car warned us before the bike fell over all the way, but it was leaning on my bike when we pulled over. The other bike wasn't so lucky, it tipped over the side of the car, held on by it's rear wheel strap, the tip of the fork broke off, and there was some other damage to the bike.
Both bikes had carbon forks, FWIW. Personally after seeing/hearing about this, I wouldn't file them unless it was on a race bike where a quick wheel change was actually important.