Little inflatables are used very regularly by tallships to assist with berthing and unberthing.
However, most don't have rigid hulls, and therefore wouldn't be risking a parting of tube and hull right at the bow with the pushing. Those that do have rigid hulls though seem to have large tyres strapped around the bow to spread the load....
When it came in this summer, I used our small dory at work with a 40hp engine to assist with the berthing of Dunbrody at the dock.
With the correct positioning, a small boat can handle a much bigger boat without a problem at all..... what you will find though is that if you are pulling the boat away from the wall, you will need to be a bit of a distance away from the vessel or your own wash will be just pushing against the hull of the boat you are trying to move, which is why it'd be far better to push.
The other week in a gale, we had to pull a large ketch just a little bit smaller than the one you're looking to move away from a wall at the top end of the dock.... the dory tried with no success, and even when I had the tug attached, I was nearly at full weight (about 3.5ton pull) before the boat started to come in my direction.
To be honest though, I wouldn't use the rib in that situation cos you "could" cause damage to it - it may be better to see if there's a small harbour launch around to assist the boat with coming away from the wall. If you're not sure, it's always best to ask for more help