Are smalltime block chains susceptible to brute force liars? My understanding is that the integrity of the bitcoin block chain is dependent on the consensus of the masses - that no single actor can write entries at will unless they. controlled over 50% of the compute power focused on calculating proofs. 

If this is true, wouldn’t small time coin with much less compute power working for it be susceptible to a bad actor, assuming this actor could focus enough resources? Specifically, slightly more than the current compute power dedicated to the coin such that the bad actor controlled greater than 50%?
Yes, many small coins are susceptible to such attacks. However, the value of the coins is so small that performing a 51% attack on the coin has almost no real use whatsoever. The coins that do actually have value where performing a 51% attack would actually result in non-negligible gains for the attacker are more difficult to attack because they are actually used.